Front-end problems are challenges designed to test and improve the skills of frontend developers in creating amazing user interfaces and experiences for web applications. These challenges can be simple or complex and simulate real-world scenarios that frontend developers might encounter in their work, giving them a chance to practice and develop their skills. To tackle these problems, developers need to be proficient in HTML, CSS, and JavaScript, as well as various libraries and frameworks used in modern web development. They also need to keep in mind user-centered design principles to create interfaces that are easy to use and intuitive.
Examples of these challenges include creating responsive layouts, making the user experience more engaging with animations and transitions, building dynamic interfaces that respond to user input, and optimizing performance for different browsers and devices. Solving these problems is crucial for frontend developers as it helps them refine their skills, become more proficient in their work, and better prepared to handle any challenges that come up in their projects. It also boosts their confidence and helps them build a great portfolio of work to show off to potential employers.
Problems
🟢 Easy Level
🟡 Average Level
🔴 Difficult Level
⚛️ React Problems
🟢 Easy Level
Problem 1
Create a simple slideshow with images that automatically advance every few seconds.
Solution:
Step 1: Create a new HTML file and add a section for the slideshow.
<!DOCTYPE html>
<html>
<head>
<title>Simple Slideshow</title>
<style>
.slideshow {
position: relative;
width: 100%;
height: 500px;
overflow: hidden;
}
.slideshow img {
position: absolute;
top: 0;
left: 0;
width: 100%;
height: 500px;
object-fit: cover;
}
</style>
</head>
<body>
<section class="slideshow">
<img src="image1.jpg" alt="Image 1">
<img src="image2.jpg" alt="Image 2">
<img src="image3.jpg" alt="Image 3">
</section>
</body>
</html>
Step 2: Add CSS styles to hide all images except the first one and set up the automatic slideshow transition.
<!DOCTYPE html>
<html>
<head>
<title>Simple Slideshow</title>
<style>
.slideshow {
position: relative;
width: 100%;
height: 500px;
overflow: hidden;
}
.slideshow img {
position: absolute;
top: 0;
left: 0;
width: 100%;
height: 500px;
object-fit: cover;
opacity: 0;
transition: opacity 1s;
}
.slideshow img:first-child {
opacity: 1;
}
</style>
</head>
<body>
<section class="slideshow">
<img src="image1.jpg" alt="Image 1">
<img src="image2.jpg" alt="Image 2">
<img src="image3.jpg" alt="Image 3">
</section>
<script>
const images = document.querySelectorAll('.slideshow img');
let currentImage = 0;
function showImage(index) {
images[currentImage].style.opacity = 0;
currentImage = (index + images.length) % images.length;
images[currentImage].style.opacity = 1;
}
setInterval(() => {
showImage(currentImage + 1);
}, 3000);
</script>
</body>
</html>
Step 3: Test the slideshow by running the HTML file in a web browser.
The slideshow should automatically transition between the images every few seconds. You can add more images to the slideshow by simply adding more ‘<img>’ tags to the HTML file.
Problem 2
Add a video to your web page that plays automatically when the page loads.
Solution:
Step 1: Create a new HTML file and add a ‘<video>’ tag to the body section.
<!DOCTYPE html>
<html>
<head>
<title>Video Player</title>
</head>
<body>
<video src="video.mp4" autoplay muted loop></video>
</body>
</html>
Step 2: Add CSS styles to center the video on the page and set the video dimensions.
<!DOCTYPE html>
<html>
<head>
<title>Video Player</title>
<style>
video {
position: absolute;
top: 50%;
left: 50%;
transform: translate(-50%, -50%);
width: 80%;
height: auto;
}
</style>
</head>
<body>
<video src="video.mp4" autoplay muted loop></video>
</body>
</html>
Step 3: Test the video player by running the HTML file in a web browser.
The video should automatically start playing when the page loads. You can change the video source by modifying the src attribute of the ‘<video>’ tag. Note that the ‘autoplay’, ‘muted’, and ‘loop’ attributes are used to ensure that the video starts playing automatically, is muted, and loops continuously.
Problem 3
Create a responsive navigation menu that collapses into a hamburger menu on smaller screens.
Solution:
Step 1: Create a basic navigation menu with an unordered list.
<!DOCTYPE html>
<html>
<head>
<title>Responsive Navigation Menu</title>
<style>
nav ul {
list-style: none;
margin: 0;
padding: 0;
display: flex;
justify-content: center;
align-items: center;
}
nav li {
margin: 0 10px;
}
nav a {
text-decoration: none;
color: #333;
font-weight: bold;
}
</style>
</head>
<body>
<nav>
<ul>
<li><a href="#">Home</a></li>
<li><a href="#">About</a></li>
<li><a href="#">Services</a></li>
<li><a href="#">Contact</a></li>
</ul>
</nav>
</body>
</html>
Step 2: Add CSS styles to create a hamburger menu on smaller screens.
<!DOCTYPE html>
<html>
<head>
<title>Responsive Navigation Menu</title>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<style>
nav ul {
list-style: none;
margin: 0;
padding: 0;
display: flex;
justify-content: center;
align-items: center;
}
nav li {
margin: 0 10px;
}
nav a {
text-decoration: none;
color: #333;
font-weight: bold;
}
nav .hamburger {
display: none;
font-size: 24px;
cursor: pointer;
}
@media (max-width: 768px) {
nav ul {
flex-direction: column;
align-items: flex-start;
}
nav li {
margin: 10px 0;
}
nav .hamburger {
display: block;
}
nav .menu {
display: none;
}
nav .menu.active {
display: block;
}
}
</style>
</head>
<body>
<nav>
<span class="hamburger">☰</span>
<ul class="menu">
<li><a href="#">Home</a></li>
<li><a href="#">About</a></li>
<li><a href="#">Services</a></li>
<li><a href="#">Contact</a></li>
</ul>
</nav>
<script>
const hamburger = document.querySelector('.hamburger');
const menu = document.querySelector('.menu');
hamburger.addEventListener('click', () => {
menu.classList.toggle('active');
});
</script>
</body>
</html>
Step 3: Test the responsive navigation menu by resizing the browser window or opening the page on a mobile device.
The navigation menu should collapse into a hamburger menu on smaller screens, and clicking the hamburger menu should expand the menu. You can modify the hamburger icon by changing the text content of the ‘.hamburger’ span element.
Problem 4
Add social media icons to your web page that link to your social media profiles.
Solution:
Step 1: Choose the social media platforms you want to link to and find appropriate icons. You can create your own icons or use pre-made icons from a website like Font Awesome.
Step 2: Add the appropriate HTML and CSS to your web page to display the social media icons.
<!DOCTYPE html>
<html>
<head>
<title>Social Media Icons</title>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css">
<style>
.social-media-icons {
display: flex;
justify-content: center;
align-items: center;
}
.social-media-icons a {
margin: 0 10px;
color: #333;
font-size: 24px;
}
.social-media-icons a:hover {
color: #3B5998;
}
</style>
</head>
<body>
<div class="social-media-icons">
<a href="https://www.facebook.com"><i class="fa fa-facebook"></i></a>
<a href="https://www.twitter.com"><i class="fa fa-twitter"></i></a>
<a href="https://www.linkedin.com"><i class="fa fa-linkedin"></i></a>
<a href="https://www.instagram.com"><i class="fa fa-instagram"></i></a>
</div>
</body>
</html>
Step 3: Test the social media icons by clicking on them to make sure they link to the correct social media profiles.
The social media icons should display on your web page, and clicking on them should redirect the user to the appropriate social media profiles. You can add or remove social media icons by modifying the HTML and CSS code.
Problem 5
Create a button that shows or hides a hidden section of your web page.
To create a button that shows or hides a hidden section of your web page, you can use HTML, CSS, and JavaScript. Here's a solution that uses the ‘onclick’ attribute and some CSS:
HTML:
<button onclick="toggleSection()">Show/Hide Section</button>
<div id="hiddenSection">
This is the hidden section
</div>
CSS:
#hiddenSection {
display: none;
}
JavaScript:
function toggleSection() {
var section = document.getElementById("hiddenSection");
if (section.style.display === "none") {
section.style.display = "block";
} else {
section.style.display = "none";
}
}
In this example, we use the ‘onclick’ attribute to add a click event listener to the button. When the button is clicked, the ‘toggleSection()’ function is called. The function gets a reference to the hidden section using ‘document.getElementById()’, and checks its current ‘display’ style property. If the ‘display’ property is set to "none", the function sets it to "block" to show the section. If it's already set to "block", the function sets it to "none" to hide the section.
The CSS rule sets the initial ‘display’ property of the hidden section to "none", so it's hidden by default. You can adjust the CSS rules as needed to style the button and hidden section.
🟡 Average Level
Problem 1
Create a Weather app that displays the current weather and a 5-day forecast.
Solution:
Step 1: Choose a weather API to use. Some popular options include OpenWeatherMap, AccuWeather, and Weather Underground. For this example, we'll use OpenWeatherMap.
Step 2: Sign up for an API key from your chosen weather API provider. This key will be used to authenticate your app and make requests to the API.
Step 3: Set up the HTML structure for the weather app. This will include a container for the current weather, a container for the 5-day forecast, and placeholders for the weather data that will be populated dynamically.
PHP
<div class="weather">
<div class="current">
<h2>Current Weather</h2>
<div class="weather-data">
<div class="temperature"></div>
<div class="conditions"></div>
</div>
</div>
<div class="forecast">
<h2>5-day Forecast</h2>
<div class="weather-data"></div>
</div>
</div>
Step 4: Write JavaScript code to fetch the current weather and 5-day forecast data from the API using the API key. Use the ‘fetch’ function to make a GET request to the API endpoint and pass in the API key as a parameter. This will return a Promise that you can use to handle the response.
JAVASCRIPT
const apiKey = 'YOUR_API_KEY';
const apiUrl = `https://api.openweathermap.org/data/2.5/forecast?id=524901&appid=${apiKey}`;fetch(apiUrl)
.then(response => response.json())
.then(data => {
// Code to handle the response data
})
.catch(error => console.error(error));
Step 5: Extract the current weather data and populate the HTML with the current temperature and conditions. The current weather data can typically be found in the ‘data.list[0]’ object. Use ‘querySelector’ to select the temperature and conditions elements and update their innerHTML to display the current weather data.
JAVASCRIPT
const currentTemp = document.querySelector('.temperature');
const currentConditions = document.querySelector('.conditions');
const currentWeatherData = data.list[0];
const currentTempValue = Math.round(currentWeatherData.main.temp - 273.15);
const currentConditionsValue = currentWeatherData.weather[0].description;
currentTemp.innerHTML = `${currentTempValue}°C`;
currentConditions.innerHTML = currentConditionsValue;
Step 6: Extract the 5-day forecast data and create HTML elements to display each day's weather data. The 5-day forecast data can be found in the ‘data.list’ array, with each element representing a 3-hour interval. To display the daily forecast, you'll need to group the 3-hour intervals by date and extract the relevant weather data. Use ‘createElement’ and ‘appendChild’ to create HTML elements for each day's weather data and add them to the forecast container.
VBNET
const forecastContainer = document.querySelector('.forecast .weather-data');// Group the 3-hour intervals by date
const forecastsByDate = data.list.reduce((forecasts, forecast) => {
const date = forecast.dt_txt.split(' ')[0];
if (!forecasts[date]) {
forecasts[date] = [];
}
forecasts[date].push(forecast);
return forecasts;
}, {});// Create HTML elements for each day's weather data
for (const date in forecastsByDate) {
const dayForecasts = forecastsByDate[date];
const day = document.createElement('div');
Problem 2
Design and implement a modal window that can be opened by clicking on a button, and closed by clicking on the overlay or a close button. The modal should have a fade-in animation when it opens and a fade-out animation when it closes. The content of the modal should be customizable and can contain any type of HTML elements.
Solution:
To create a modal window with animations and customizable content, we'll need to use HTML, CSS, and JavaScript. Here are the steps to implement the solution:
Step 1: Create a button that will open the modal window. For example, you can create a button with the text "Open Modal" and an ID of "open-modal-btn".
HTML
<button id="open-modal-btn">Open Modal</button>
Step 2: Create the HTML structure for the modal window. This will consist of a container div with a semi-transparent overlay, and a content div for the actual modal content. Add a close button to the top-right corner of the modal.
HTML
<div id="modal-container">
<div id="modal-overlay"></div>
<div id="modal-content">
<button id="close-modal-btn">×</button>
<p>Modal content goes here.</p>
</div>
</div>
Step 3: Style the modal container and content with CSS. Position the modal container in the center of the screen and give it a higher z-index than the other page elements. Style the overlay to be semi-transparent and cover the entire screen.
CSS
#modal-container {
position: fixed;
top: 50%;
left: 50%;
transform: translate(-50%, -50%);
z-index: 9999;
display: none;
}
#modal-overlay {
position: fixed;
top: 0;
left: 0;
width: 100%;
height: 100%;
background-color: rgba(0, 0, 0, 0.5);
}
#modal-content {
background-color: #fff;
padding: 20px;
border-radius: 5px;
box-shadow: 0 0 10px rgba(0, 0, 0, 0.5);
position: relative;
}
#close-modal-btn {
position: absolute;
top: 10px;
right: 10px;
font-size: 24px;
border: none;
background: none;
cursor: pointer;
}
Step 4: Use JavaScript to add event listeners to the open and close buttons, and to control the opening and closing of the modal. When the open button is clicked, the modal container should be displayed and the fade-in animation should be triggered. When the close button or overlay is clicked, the modal container should be hidden and the fade-out animation should be triggered.
Problem 3
Create a sign-up form with real-time username availability check and password strength meter.
Solution:
Step 1: Create an HTML form that includes input fields for the user's name, email address, username, password, and password confirmation.
HTML
<form>
<label for="name">Name:</label>
<input type="text" id="name" name="name" required>
<label for="email">Email:</label>
<input type="email" id="email" name="email" required>
<label for="username">Username:</label>
<input type="text" id="username" name="username" required>
<label for="password">Password:</label>
<input type="password" id="password" name="password" required>
<label for="password-confirm">Confirm Password:</label>
<input type="password" id="password-confirm" name="password-confirm" required>
<button type="submit">Sign up</button>
</form>
Step 2: Add a real-time username availability check. You can achieve this by using JavaScript to make an asynchronous call to the server that checks whether the entered username is available. In the example below, we're using jQuery to make the AJAX call and display the response.
HTML
<label for="username">Username:</label>
<input type="text" id="username" name="username" required>
<div id="username-status"></div>
<script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>
<script>
$('#username').on('input', function() {
const username = $(this).val();
$.get(`/check-username?username=${username}`, function(response) {
const status = $('#username-status');
if (response === 'available') {
status.text('Username is available!');
} else {
status.text('Username is taken.');
}
});
});
</script>
On the server side, you need to implement the ‘/check-username’ endpoint that performs the username availability check and returns a response.
JAVASCRIPT
app.get('/check-username', (req, res) => {
const { username } = req.query;
if (username === 'john') {
res.send('taken');
} else {
res.send('available');
}
});
Step 3: Add a password strength meter. You can use a library like zxcvbn to estimate the strength of the entered password and display the result to the user. In the example below, we're using the ‘zxcvbn’ library to estimate the password strength and display a visual indicator of the strength.
HTML
<label for="password">Password:</label>
<input type="password" id="password" name="password" required>
<div id="password-strength"></div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/zxcvbn/4.4.2/zxcvbn.js"></script>
<script>
$('#password').on('input', function() {
const password = $(this).val();
const result = zxcvbn(password);
const strength = result.score + 1; // score is between 0 and 4
const indicators = ['Very weak', 'Weak', 'Moderate', 'Strong', 'Very strong'];
const indicator = indicators[strength];
const bar = $('<div>').addClass(`strength-${strength}`).text(indicator);
$('#password-strength').empty().append(bar);
});
</script>
``
Problem 4
Build a chat widget with real-time messaging and user authentication.
Solution:
Step 1: Choose a backend technology to handle real-time messaging and user authentication. Some popular choices include Node.js, Firebase, and PubNub.
Step 2: Create a database to store user information, messages, and any other relevant data.
Step 3: Set up user authentication to allow users to sign up and log in to the chat widget. You can use a third-party service like Google, Facebook, or Twitter to simplify the implementation.
Step 4: Implement real-time messaging using a library like Socket.IO. Socket.IO provides a simple API for sending and receiving messages in real-time.
JAVASCRIPT
// server.js
const app = require("express")();
const http = require("http").createServer(app);
const io = require("socket.io")(http);
io.on("connection", (socket) => {
console.log("a user connected");
socket.on("message", (msg) => {
console.log("message: " + msg);
io.emit("message", msg);
});
socket.on("disconnect", () => {
console.log("user disconnected");
});
});
http.listen(3000, () => {
console.log("listening on *:3000");
});
HTML
<!-- client.html -->
<div id="messages"></div>
<form id="chat-form">
<input id="message-input" type="text">
<button type="submit">Send</button>
</form>
<script src="/socket.io/socket.io.js"></script>
<script>
const socket = io();
socket.on("message", (msg) => {
const messageElement = document.createElement("div");
messageElement.textContent = msg;
document.getElementById("messages").appendChild(messageElement);
});
document.getElementById("chat-form").addEventListener("submit", (event) => {
event.preventDefault();
const input = document.getElementById("message-input");
const message = input.value;
input.value = "";
socket.emit("message", message);
});
</script>
Step 5: Implement the chat widget in your web page. You can use HTML, CSS, and JavaScript to create a user interface that allows users to send and receive messages in real-time.
The resulting web page should allow authenticated users to send and receive messages in real-time. The ‘socket.io’ library enables real-time communication between the server and the client, while user authentication ensures that only authorized users can access the chat widget.
Problem 5
Design and implement a drag-and-drop interface for organizing and reordering elements on a web page.
Solution:
Step 1: Choose the elements you want to drag and drop, and give them unique IDs to make them identifiable.
HTML
<div class="container">
<div class="item" id="item1">Item 1</div>
<div class="item" id="item2">Item 2</div>
<div class="item" id="item3">Item 3</div>
<div class="item" id="item4">Item 4</div>
<div class="item" id="item5">Item 5</div>
</div>
Step 2: Add JavaScript to enable drag and drop functionality. You can use the HTML5 drag and drop API or a library like jQuery UI to simplify the implementation.
HTML
<script>
$(function() {
$(".item").draggable({
revert: "invalid",
helper: "clone",
cursor: "move"
});
$(".container").droppable({
drop: function(event, ui) {
var droppedItem = ui.draggable;
var droppedOn = $(this);
if (!droppedOn.has(droppedItem).length) {
droppedItem.detach().appendTo(droppedOn);
}
}
});
});
</script>
Step 3: Style the elements and add any additional functionality as needed.
CSS
.container {
display: flex;
flex-wrap: wrap;
justify-content: space-between;
}
.item {
background-color: #eee;
border: 1px solid #ccc;
padding: 10px;
margin: 10px;
cursor: pointer;
}
The resulting web page should allow the user to drag and drop the elements within the container to reorganize them. The ‘helper’ option in the draggable function creates a clone of the item being dragged, while the ‘revert’ option ensures that the item snaps back to its original position if it is not dropped on a valid target. The ‘drop’ function in the droppable function detaches the dropped item from its original position and appends it to the new position within the container.
🔴 Difficult Level
Problem 1
You are tasked with creating a responsive navigation menu for a website that needs to work on both desktop and mobile devices. The menu should have dropdown menus that work correctly on touchscreens. The design of the menu should also be flexible and adaptable to different screen sizes.
Solution:
Step 1: Create the HTML structure for the navigation menu.
PHP
<nav class="navigation">
<ul>
<li><a href="#">Home</a></li>
<li><a href="#">About Us</a></li>
<li>
<a href="#">Services</a>
<ul>
<li><a href="#">Service 1</a></li>
<li><a href="#">Service 2</a></li>
<li><a href="#">Service 3</a></li>
</ul>
</li>
<li><a href="#">Contact Us</a></li>
</ul>
</nav>
Step 2: Add CSS to style the navigation menu and make it responsive.
CSS
.navigation {
background-color: #333;
display: flex;
justify-content: space-between;
align-items: center;
height: 80px;
padding: 0 20px;
}
.navigation ul {
list-style: none;
margin: 0;
padding: 0;
display: flex;
align-items: center;
}
.navigation li {
margin: 0 10px;
position: relative;
}
.navigation a {
color: #fff;
text-decoration: none;
padding: 10px;
display: block;
}
.navigation ul ul {
position: absolute;
top: 100%;
left: 0;
background-color: #333;
display: none;
z-index: 1;
}
.navigation ul ul li {
width: 100%;
}
.navigation ul ul a {
padding: 10px;
}
.navigation li:hover > ul {
display: block;
}
@media (max-width: 768px) {
.navigation {
flex-direction: column;
height: auto;
}
.navigation ul {
flex-direction: column;
}
.navigation li {
margin: 10px 0;
}
.navigation li:hover > ul {
display: block;
position: static;
}
}
Step 3: Add JavaScript to make the dropdown menus work on touchscreens.
JAVASCRIPT
(function() {
var touch = false;
if ('ontouchstart' in window) {
touch = true;
}
if (touch === true) {
$('.navigation li').on('click', function() {
if ($(this).hasClass('active')) {
$(this).removeClass('active');
} else {
$('.navigation li').removeClass('active');
$(this).addClass('active');
}
});
}
})();
This JavaScript code detects whether the user is on a touchscreen device and adds a click event listener to the navigation menu items. When the user clicks on a menu item, it adds the 'active' class to that item, which causes the dropdown menu to display.
With these HTML, CSS, and JavaScript changes, the navigation menu should now be responsive and support dropdown menus on touchscreens. The menu design is also flexible and adaptable to different screen sizes.
Problem 2
You are tasked with creating a complex form that requires multiple validation rules, custom input types, and conditional fields that appear based on user input. The form should be user-friendly and intuitive, and should help guide the user through the submission process.
Solution:
Step 1: Create the HTML structure for the form.
PHP
<form id="myForm" action="#" method="post">
<fieldset>
<legend>Contact Information</legend>
<label for="name">Name:</label>
<input type="text" id="name" name="name" required>
<label for="email">Email:</label>
<input type="email" id="email" name="email" required>
<label for="phone">Phone:</label>
<input type="tel" id="phone" name="phone" pattern="[0-9]{3}-[0-9]{3}-[0-9]{4}" required>
<label for="gender">Gender:</label>
<select id="gender" name="gender" required>
<option value="">Select Gender</option>
<option value="male">Male</option>
<option value="female">Female</option>
<option value="other">Other</option>
</select>
<label for="age">Age:</label>
<input type="number" id="age" name="age" min="18" max="100" required>
</fieldset>
<fieldset>
<legend>Account Information</legend>
<label for="username">Username:</label>
<input type="text" id="username" name="username" required>
<label for="password">Password:</label>
<input type="password" id="password" name="password" required>
<label for="confirm-password">Confirm Password:</label>
<input type="password" id="confirm-password" name="confirm-password" required>
</fieldset>
<fieldset>
<legend>Additional Information</legend>
<label for="interests">Interests:</label>
<textarea id="interests" name="interests"></textarea>
<label for="newsletter">Sign up for our newsletter:</label>
<input type="checkbox" id="newsletter" name="newsletter" value="true">
<div id="newsletter-details">
<label for="newsletter-email">Email:</label>
<input type="email" id="newsletter-email" name="newsletter-email">
</div>
</fieldset>
<button type="submit">Submit</button>
</form>
Step 2: Add CSS to style the form and make it user-friendly.
CSS
form {
margin: 0 auto;
max-width: 600px;
}
fieldset {
margin: 20px 0;
padding: 10px;
border: 1px solid #ccc;
border-radius: 5px;
}
legend {
font-size: 1.2em;
font-weight: bold;
}
label {
display: block;
margin-bottom: 5px;
}
input[type="text"],
input[type="email"],
input[type="tel"],
input[type="password"],
textarea {
width: 100%;
padding: 10px;
border: 1px solid #ccc;
border-radius: 5px;
margin-bottom: 10px;
}
select {
width: 100%;
padding: 10px;
Problem 3
You are tasked with building a table that has dynamic sorting and filtering functionality, which should allow users to sort the table data by clicking on table headers, and filter the table data by typing into an input field. The table should also update without requiring the page to be reloaded.
Solution:
Step 1: Create the HTML structure for the table.
PHP
<table id="myTable">
<thead>
<tr>
<th>Name</th>
<th>Age</th>
<th>Country</th>
<th>Salary</th>
</tr>
</thead>
<tbody>
<tr>
<td>John</td>
<td>25</td>
<td>USA</td>
<td>$60,000</td>
</tr>
<tr>
<td>Mary</td>
<td>30</td>
<td>Canada</td>
<td>$70,000</td>
</tr>
<tr>
<td>David</td>
<td>35</td>
<td>UK</td>
<td>$80,000</td>
</tr>
<tr>
<td>Sarah</td>
<td>28</td>
<td>USA</td>
<td>$75,000</td>
</tr>
</tbody>
</table>
Step 2: Add CSS to style the table and make it user-friendly.
CSS
table {
border-collapse: collapse;
width: 100%;
}
th, td {
text-align: left;
padding: 8px;
border-bottom: 1px solid #ddd;
}
th {
cursor: pointer;
}
tr:hover {
background-color: #f5f5f5;
}
Step 3: Add JavaScript to make the table dynamic.
JAVASCRIPT
// Get the table and table body
const table = document.getElementById("myTable");
const tbody = table.getElementsByTagName("tbody")[0];
// Get the table headers and create an array of objects to store the sorting state
const headers = table.getElementsByTagName("th");
const sorting = Array.from(headers).map(header => ({
header,
sortState: null
}));
// Add event listeners to the table headers to allow sorting
headers.forEach((header, index) => {
header.addEventListener("click", () => {
// Update the sorting state for this column
sorting[index].sortState = sorting[index].sortState === "asc" ? "desc" : "asc";
// Sort the table data based on the current sorting state
const rows = Array.from(tbody.rows);
rows.sort((a, b) => {
const aValue = a.cells[index].textContent;
const bValue = b.cells[index].textContent;
if (sorting[index].sortState === "asc") {
return aValue.localeCompare(bValue);
} else {
return bValue.localeCompare(aValue);
}
});
// Add the sorted rows back to the table
rows.forEach(row => tbody.appendChild(row));
});
});
// Add event listener to the filter input to allow filtering
const filterInput = document.getElementById("filterInput");
filterInput.addEventListener("input", () => {
const filterText = filterInput.value.toLowerCase();
// Filter the table data based on the filter text
const rows = Array.from(tbody.rows);
rows.forEach(row => {
const shouldHide = Array
Problem 4
You need to create a multi-step form that has different form fields and layout based on user input. Each step should be displayed one at a time, and users should be able to navigate between the steps using next and back buttons.
Solution:
Step 1: Create the HTML structure for the form.
PHP
<form id="myForm">
<div id="step1">
<label for="name">Name:</label>
<input type="text" id="name" name="name">
<button id="nextStep1">Next</button>
</div>
<div id="step2" style="display: none;">
<label for="email">Email:</label>
<input type="email" id="email" name="email">
<button id="backStep2">Back</button>
<button id="nextStep2">Next</button>
</div>
<div id="step3" style="display: none;">
<label for="password">Password:</label>
<input type="password" id="password" name="password">
<button id="backStep3">Back</button>
<button type="submit">Submit</button>
</div>
</form>
Step 2: Add CSS to style the form and make it user-friendly.
CSS
form {
max-width: 400px;
margin: 0 auto;
}
label, input {
display: block;
margin-bottom: 10px;
}
button {
margin-top: 10px;
}
.hide {
display: none;
}
Step 3: Add JavaScript to make the form dynamic.
JAVASCRIPT
// Get the form and all form steps
const form = document.getElementById("myForm");
const steps = Array.from(form.children);
// Add event listeners to the next and back buttons for each step
for (let i = 0; i < steps.length; i++) {
const step = steps[i];
const nextBtn = step.querySelector(`#nextStep${i + 1}`);
const backBtn = step.querySelector(`#backStep${i + 1}`);
if (nextBtn) {
nextBtn.addEventListener("click", (event) => {
event.preventDefault();
// Check if the current step is valid
const isValid = validateStep(step);
if (isValid) {
// Hide the current step and show the next step
step.classList.add("hide");
steps[i + 1].classList.remove("hide");
}
});
}
if (backBtn) {
backBtn.addEventListener("click", (event) => {
event.preventDefault();
// Hide the current step and show the previous step
step.classList.add("hide");
steps[i - 1].classList.remove("hide");
});
}
}
// Add event listener to the form to handle submission
form.addEventListener("submit", (event) => {
event.preventDefault();
// Get the form data and log it to the console
const formData = new FormData(form);
const data = Object.fromEntries(formData.entries());
console.log(data);
});
// Add function to validate each step
function validateStep(step) {
const inputs = Array.from(step.querySelectorAll("input"));
let isValid = true;
inputs.forEach(input => {
const validity = input.checkValidity();
if (!validity) {
input.reportValidity();
isValid = false;
}
});
return isValid;
}
Problem 5
You need to create a custom HTML video player that includes advanced playback controls, such as support for subtitles, multiple audio tracks, and dynamic bitrate switching.
Solution:
Step 1: Create the HTML structure for the video player.
PHP
<div class="video-player">
<video controls>
<source src="my-video.mp4" type="video/mp4">
<source src="my-video.webm" type="video/webm">
<track label="English" kind="subtitles" src="my-video-en.vtt" srclang="en" default>
<track label="Français" kind="subtitles" src="my-video-fr.vtt" srclang="fr">
</video>
<div class="controls">
<button class="play-pause"></button>
<div class="time">
<span class="current-time">0:00</span>
<div class="progress">
<div class="progress-bar"></div>
</div>
<span class="duration">0:00</span>
</div>
<button class="fullscreen"></button>
<button class="audio-track"></button>
<button class="subtitles"></button>
<button class="quality"></button>
</div>
</div>
Step 2: Add CSS to style the video player.
CSS
.video-player {
position: relative;
width: 100%;
height: 0;
padding-top: 56.25%;
}
.video-player video {
position: absolute;
top: 0;
left: 0;
width: 100%;
height: 100%;
}
.video-player .controls {
position: absolute;
bottom: 0;
left: 0;
width: 100%;
background: rgba(0, 0, 0, 0.5);
}
.video-player .controls button {
background: none;
border: none;
color: #fff;
font-size: 16px;
margin: 5px;
}
.video-player .controls button:hover {
cursor: pointer;
}
.video-player .controls .time {
display: inline-block;
color: #fff;
font-size: 14px;
margin: 5px;
}
.video-player .controls .progress {
display: inline-block;
width: 50%;
height: 10px;
background: #333;
margin: 0 10px;
position: relative;
top: 2px;
}
.video-player .controls .progress-bar {
position: absolute;
top: 0;
left: 0;
width: 0%;
height: 100%;
background: #fff;
}
.video-player .controls .fullscreen,
.video-player .controls .audio-track,
.video-player .controls .subtitles,
.video-player .controls .quality {
float: right;
}
.video-player .controls .fullscreen::before {
content: "\f065";
font-family: "Font Awesome 5 Free";
font-weight: 900;
}
.video-player .controls .play-pause::before {
content: "\f04b";
font-family: "Font Awesome 5 Free";
font-weight: 900;
}
.video-player .controls .play-pause.paused::before {
content: "\f04c";
}
.video-player .controls .audio-track::before {
content: "\f028";
font-family: "Font Awesome 5 Free";
font-weight:
Problem 6
Build a web-based chatbot that can understand natural language and respond to user queries using machine learning.
Solution:
To build a web-based chatbot with natural language processing and machine learning capabilities, we can use the following steps:
Step 1: Choose a natural language processing library
There are many natural language processing libraries available, such as spaCy, NLTK, and StanfordNLP. For this example, we will use the spaCy library, which provides easy-to-use tools for natural language processing and is compatible with many machine learning libraries.
Step 2: Train the chatbot using machine learning
To train the chatbot, we can use a machine learning library like TensorFlow or PyTorch. In this example, we will use TensorFlow, which provides a high-level API for building and training machine learning models.
Step 3: Build the chatbot interface
We can build the chatbot interface using web development tools like HTML, CSS, and JavaScript. For this example, we will use the React library to build a simple chat interface.
Step 4: Connect the chatbot to the interface
To connect the chatbot to the interface, we will use a WebSocket to send and receive messages between the client and server. On the server side, we will use Node.js and Express to handle WebSocket connections and serve the chatbot API.
Here's an example code implementation using the technologies and libraries mentioned above:
JAVASCRIPT
// Import necessary libraries and modules
const express = require('express');
const http = require('http');
const WebSocket = require('ws');
const spacy = require('spacy');
const tf = require('@tensorflow/tfjs-node');
// Initialize the chatbot
const nlp = await spacy.load('en_core_web_sm');
const model = await tf.loadLayersModel('model.json');
// Define a function to process user messages
async function processMessage(message) {
// Use spaCy to tokenize the message
const doc = await nlp(message);
const tokens = doc.tokens.map(token => token.lemma_);
// Convert the tokens to a tensor and make a prediction using the model
const tensor = tf.tensor2d(tokens, [1, tokens.length]);
const prediction = model.predict(tensor);
// Get the index of the predicted intent and return the response
const intentIndex = tf.argMax(prediction).dataSync()[0];
const response = intents[intentIndex].response;
return response;
}
// Define the chatbot intents
const intents = [
{
tag: 'greeting',
patterns: ['hello', 'hi', 'hey'],
response: 'Hello! How can I help you today?'
},
{
tag: 'goodbye',
patterns: ['bye', 'goodbye', 'see you later'],
response: 'Goodbye! Have a great day!'
},
{
tag: 'thanks',
patterns: ['thanks', 'thank you'],
response: 'You\'re welcome! Is there anything else I can help you with?'
},
{
tag: 'unknown',
patterns: [''],
response: 'Sorry, I didn\'t understand that. Can you please rephrase your question?'
}
];
// Set up the server and WebSocket connection
const app = express();
const server = http.createServer(app);
const wss = new WebSocket.Server({ server });
// Handle WebSocket connections
wss.on('connection', function connection(ws) {
ws.on('message', async function incoming(message) {
// Process the user message and send the response back to the client
const
⚛️ React Problems
Problem 1
Write a React component that renders a list of items from an array. The component should take an array of items as a prop, and render each item as a list item.
Solution:
We can create a functional component called ItemList that takes an array of items as a prop and uses the map method to render each item as a list item. Here's the code for the ItemList component:
JSX
import React from 'react';
function ItemList(props) {
const items = props.items.map((item) => <li key={item.id}>{item.name}</li>);
return (
<div>
<h2>Items:</h2>
<ul>{items}</ul>
</div>
);
}
export default ItemList;
In this code, we first use the map method to create a new array of list item elements for each item in the props.items array. We also use the key prop to ensure that each list item has a unique identifier.
Then, we render the list of items using an unordered list (<ul>) and wrap it in a div element that includes a header (<h2>) to display the title "Items".
Finally, we export the ItemList component as the default export of this module.
To use the ItemList component in another part of our application, we can import it and pass an array of items as a prop like this:
JSX
import React from 'react';
import ItemList from './ItemList';
function App() {
const items = [
{ id: 1, name: 'Item 1' },
{ id: 2, name: 'Item 2' },
{ id: 3, name: 'Item 3' },
];
return (
<div>
<h1>My App</h1>
<ItemList items={items} />
</div>
);
}
export default App;
In this example, we create an array of items and pass it as a prop to the ItemList component, which then renders the list of items as list items.
Problem 2
Create a form component that allows a user to input a username and password. When the form is submitted, validate the input and display an error message if either field is empty.
Solution:
We can create a class component called LoginForm that has two input fields, one for the username and one for the password. We'll also add a submit button that will trigger the validation logic. Here's the code for the LoginForm component:
JSX
import React, { Component } from 'react';
class LoginForm extends Component {
state = {
username: '',
password: '',
error: '',
};
handleSubmit = (event) => {
event.preventDefault();
const { username, password } = this.state;
if (!username || !password) {
this.setState({ error: 'Please enter both a username and password' });
} else {
this.setState({ error: '' });
console.log(`Submitting username ${username} and password ${password}`);
}
};
handleUsernameChange = (event) => {
this.setState({ username: event.target.value });
};
handlePasswordChange = (event) => {
this.setState({ password: event.target.value });
};
render() {
const { username, password, error } = this.state;
return (
<form onSubmit={this.handleSubmit}>
{error && <div>{error}</div>}
<div>
<label>
Username:
<input type="text" value={username} onChange={this.handleUsernameChange} />
</label>
</div>
<div>
<label>
Password:
<input type="password" value={password} onChange={this.handlePasswordChange} />
</label>
</div>
<button type="submit">Submit</button>
</form>
);
}
}
export default LoginForm;
In this code, we define the initial state of the component to include empty strings for the username and password fields, and an empty string for the error message.
We also define three methods:
handleSubmit: This method is called when the form is submitted. It first prevents the default form submission behavior, then checks if either the username or password fields are empty. If either field is empty, it sets the error message state to a non-empty string. Otherwise, it logs the username and password to the console and clears the error message state.
handleUsernameChange and handlePasswordChange: These methods are called when the user types in the respective input fields. They update the corresponding state values with the user input.
In the render method, we display the form with two input fields for the username and password, and a submit button. We also display the error message if it exists.
To use the LoginForm component in another part of our application, we can import it and add it to our App component like this:
JSX
import React from 'react';
import LoginForm from './LoginForm';
function App() {
return (
<div>
<h1>My App</h1>
<LoginForm />
</div>
);
}
export default App;
In this example, we simply render the LoginForm component inside the App component. When the user submits the form with an empty username or password field, an error message will be displayed above the form. If both fields are filled in, the username and password will be logged to the console.
Problem 3
Write a React component that renders a simple calculator. The component should have buttons for the basic arithmetic operations (+, -, *, /) and should be able to perform calculations on user input.
Solution:
We can create a class component called Calculator that has a state value to store the user input and a method to perform calculations based on the user input. Here's the code for the Calculator component:
JSX
import React, { Component } from 'react';
class Calculator extends Component {
state = {
input: '',
result: '',
};
handleInput = (event) => {
this.setState({ input: event.target.value });
};
handleCalculate = (event) => {
event.preventDefault();
const { input } = this.state;
try {
const result = eval(input);
this.setState({ result });
} catch (e) {
this.setState({ result: 'Invalid input' });
}
};
handleClear = () => {
this.setState({ input: '', result: '' });
};
render() {
const { input, result } = this.state;
return (
<div>
<form onSubmit={this.handleCalculate}>
<input type="text" value={input} onChange={this.handleInput} />
<button type="submit">Calculate</button>
<button type="button" onClick={this.handleClear}>
Clear
</button>
</form>
<div>{result}</div>
</div>
);
}
}
export default Calculator;
In this code, we define the initial state of the component to include empty strings for the user input and the result of the calculation.
We also define three methods:
handleInput: This method is called when the user types into the input field. It updates the input state with the user input.
handleCalculate: This method is called when the user clicks the "Calculate" button. It first prevents the default form submission behavior, then tries to evaluate the user input using the eval function. If the input is valid, it sets the result state to the evaluated result. If the input is not valid, it sets the result state to "Invalid input".
handleClear: This method is called when the user clicks the "Clear" button. It clears the input and result states.
In the render method, we display the calculator as a form with an input field for the user input, a "Calculate" button to perform the calculation, and a "Clear" button to clear the input and result. We also display the result of the calculation below the form.
To use the Calculator component in another part of our application, we can import it and add it to our App component like this:
JSX
import React from 'react';
import Calculator from './Calculator';
function App() {
return (
<div>
<h1>My App</h1>
<Calculator />
</div>
);
}
export default App;
In this example, we simply render the Calculator component inside the App component. When the user types in a valid arithmetic expression and clicks the "Calculate" button, the result will be displayed below the input field. If the input is invalid, the "Invalid input" message will be displayed instead.
Problem 4
Build a React component that displays a random quote when a button is clicked. The component should fetch quotes from an external API and update the UI with a new quote on each click.
Solution:
We can create a class component called QuoteGenerator that fetches random quotes from an external API and updates the UI with a new quote when the user clicks a button. Here's the code for the QuoteGenerator component:
JSX
import React, { Component } from 'react';
class QuoteGenerator extends Component {
state = {
quote: '',
author: '',
};
componentDidMount() {
this.fetchQuote();
}
fetchQuote = async () => {
try {
const response = await fetch('https://api.quotable.io/random');
const data = await response.json();
this.setState({ quote: data.content, author: data.author });
} catch (error) {
console.log(error);
}
};
handleButtonClick = () => {
this.fetchQuote();
};
render() {
const { quote, author } = this.state;
return (
<div>
<h2>Random Quote Generator</h2>
<blockquote>
<p>{quote}</p>
<footer>{author}</footer>
</blockquote>
<button onClick={this.handleButtonClick}>Generate Quote</button>
</div>
);
}
}
export default QuoteGenerator;
In this code, we define the initial state of the component to include empty strings for the quote and author.
We also define three methods:
componentDidMount: This method is called when the component is first mounted. It calls the fetchQuote method to get an initial quote to display.
fetchQuote: This method makes a request to the external API to get a random quote. If the request is successful, it updates the state with the quote and author data. If the request fails, it logs an error message to the console.
handleButtonClick: This method is called when the user clicks the "Generate Quote" button. It simply calls the fetchQuote method to get a new quote to display.
In the render method, we display the component as a heading, a blockquote with the quote and author data, and a "Generate Quote" button. When the user clicks the button, a new quote will be fetched and displayed in the UI.
To use the QuoteGenerator component in another part of our application, we can import it and add it to our App component like this:
JSX
import React from 'react';
import QuoteGenerator from './QuoteGenerator';
function App() {
return (
<div>
<h1>My App</h1>
<QuoteGenerator />
</div>
);
}
export default App;
Problem 5
Create a React component that allows a user to add and remove items from a shopping cart. The component should display the current cart items, their prices, and a total cost. The user should be able to add and remove items by clicking buttons.
Solution:
We can create a class component called ShoppingCart that manages a list of cart items and their prices. Here's the code for the ShoppingCart component:
JSX
import React, { Component } from 'react';
class ShoppingCart extends Component {
state = {
items: [],
};
addItem = (item) => {
this.setState((prevState) => ({
items: [...prevState.items, item],
}));
};
removeItem = (index) => {
this.setState((prevState) => ({
items: [...prevState.items.slice(0, index), ...prevState.items.slice(index + 1)],
}));
};
getTotalCost = () => {
const totalCost = this.state.items.reduce((acc, item) => acc + item.price, 0);
return totalCost.toFixed(2);
};
render() {
return (
<div>
<h2>Shopping Cart</h2>
<ul>
{this.state.items.map((item, index) => (
<li key={index}>
{item.name} - ${item.price.toFixed(2)}
<button onClick={() => this.removeItem(index)}>Remove</button>
</li>
))}
</ul>
<p>Total Cost: ${this.getTotalCost()}</p>
<button onClick={() => this.addItem({ name: 'Item', price: 9.99 })}>Add Item</button>
</div>
);
}
}
export default ShoppingCart;
In this code, we define the initial state of the component to include an empty array of items.
We also define four methods:
addItem: This method takes an item object as an argument and adds it to the list of cart items in the state.
removeItem: This method takes an index as an argument and removes the item at that index from the list of cart items in the state.
getTotalCost: This method calculates the total cost of all items in the cart by using the reduce method to add up the prices of all items.
In the render method, we display the component as a heading, a list of cart items and their prices, a total cost, and a button to add a new item to the cart. Each cart item is displayed with its name and price, along with a "Remove" button that calls the removeItem method when clicked.
To use the ShoppingCart component in another part of our application, we can import it and add it to our App component like this:
JSX
import React from 'react';
import ShoppingCart from './ShoppingCart';
function App() {
return (
<div>
<h1>My App</h1>
<ShoppingCart />
</div>
);
}
export default App;
In this example, we simply render the ShoppingCart component inside the App component. The user can add and remove items from the cart by clicking buttons, and the total cost of all items in the cart is displayed in the UI.
Problem 6
Write a React component that implements a drag-and-drop interface. The component should allow the user to drag items from one list to another, and should update the UI in real-time.
Solution:
We can create a class component called DragAndDrop that manages two lists of items and their drag-and-drop behavior. Here's the code for the DragAndDrop component:
JSX
import React, { Component } from 'react';
class DragAndDrop extends Component {
state = {
list1: ['Item 1', 'Item 2', 'Item 3'],
list2: ['Item 4', 'Item 5', 'Item 6'],
};
onDragStart = (event, item) => {
event.dataTransfer.setData('item', item);
};
onDragOver = (event) => {
event.preventDefault();
};
onDrop = (event, listName) => {
const item = event.dataTransfer.getData('item');
const list = [...this.state[listName]];
list.push(item);
this.setState({ [listName]: list });
};
render() {
return (
<div>
<h2>List 1</h2>
<ul onDragOver={this.onDragOver} onDrop={(event) => this.onDrop(event, 'list1')}>
{this.state.list1.map((item) => (
<li key={item} draggable onDragStart={(event) => this.onDragStart(event, item)}>
{item}
</li>
))}
</ul>
<h2>List 2</h2>
<ul onDragOver={this.onDragOver} onDrop={(event) => this.onDrop(event, 'list2')}>
{this.state.list2.map((item) => (
<li key={item} draggable onDragStart={(event) => this.onDragStart(event, item)}>
{item}
</li>
))}
</ul>
</div>
);
}
}
export default DragAndDrop;
In this code, we define the initial state of the component to include two lists of items.
We also define three methods:
onDragStart: This method is called when an item is dragged. It sets the data for the item being dragged in the data transfer object.
onDragOver: This method is called when an item is being dragged over the drop zone. It prevents the default behavior of the event to allow the item to be dropped.
onDrop: This method is called when an item is dropped onto a drop zone. It gets the item data from the data transfer object and updates the appropriate list in the state.
In the render method, we display the component as two lists with draggable items. Each item is displayed with its name and can be dragged to the other list.
To use the DragAndDrop component in another part of our application, we can import it and add it to our App component like this:
JSX
import React from 'react';
import DragAndDrop from './DragAndDrop';
function App() {
return (
<div>
<h1>My App</h1>
<DragAndDrop />
</div>
);
}
export default App;
In this example, we simply render the DragAndDrop component inside the App component. The user can drag items from one list to another, and the UI is updated in real-time.
Problem 7
Create a React component that implements a dynamic search bar. The component should fetch data from an external API and display search results in real-time as the user types in the search bar.
Solution:
We can create a class component called SearchBar that manages the search bar behavior and the fetched data from the external API. Here's the code for the SearchBar component:
JSX
import React, { Component } from 'react';
class SearchBar extends Component {
state = {
searchTerm: '',
searchResults: [],
};
onInputChange = async (event) => {
const searchTerm = event.target.value;
this.setState({ searchTerm });
if (searchTerm.trim() !== '') {
const response = await fetch(`https://api.example.com/search?q=${searchTerm}`);
const data = await response.json();
this.setState({ searchResults: data.results });
} else {
this.setState({ searchResults: [] });
}
};
render() {
return (
<div>
<input type="text" value={this.state.searchTerm} onChange={this.onInputChange} />
<ul>
{this.state.searchResults.map((result) => (
<li key={result.id}>{result.name}</li>
))}
</ul>
</div>
);
}
}
export default SearchBar;
In this code, we define the initial state of the component to include an empty searchTerm and an empty searchResults array.
We also define a method called onInputChange that is called every time the input value changes. This method sets the value of searchTerm in the state and fetches data from the external API using the searchTerm value. If the search term is empty, the search results are cleared.
In the render method, we display the component as an input field and a list of search results. The search results are displayed using the map method on the searchResults array.
To use the SearchBar component in another part of our application, we can import it and add it to our App component like this:
JSX
import React from 'react';
import SearchBar from './SearchBar';
function App() {
return (
<div>
<h1>My App</h1>
<SearchBar />
</div>
);
}
export default App;
In this example, we simply render the SearchBar component inside the App component. As the user types in the search bar, the component fetches data from the external API and displays search results in real-time.
Problem 8
Build a React component that implements a complex form with conditional fields. The form should have different fields that are displayed based on user input, and should validate input before submission.
Solution:
We can create a class component called ComplexForm that manages the form behavior and validation. Here's the code for the ComplexForm component:
JSX
import React, { Component } from 'react';
class ComplexForm extends Component {
state = {
name: '',
email: '',
phone: '',
newsletter: false,
hasPets: false,
petName: '',
petType: '',
errors: [],
};
handleSubmit = (event) => {
event.preventDefault();
const errors = [];
if (this.state.name.trim() === '') {
errors.push('Name is required');
}
if (this.state.email.trim() === '') {
errors.push('Email is required');
}
if (this.state.phone.trim() === '') {
errors.push('Phone is required');
}
if (this.state.hasPets && this.state.petName.trim() === '') {
errors.push('Pet name is required');
}
if (this.state.hasPets && this.state.petType.trim() === '') {
errors.push('Pet type is required');
}
if (errors.length > 0) {
this.setState({ errors });
} else {
// submit form data
}
};
handleNameChange = (event) => {
this.setState({ name: event.target.value });
};
handleEmailChange = (event) => {
this.setState({ email: event.target.value });
};
handlePhoneChange = (event) => {
this.setState({ phone: event.target.value });
};
handleNewsletterChange = (event) => {
this.setState({ newsletter: event.target.checked });
};
handleHasPetsChange = (event) => {
this.setState({ hasPets: event.target.checked });
};
handlePetNameChange = (event) => {
this.setState({ petName: event.target.value });
};
handlePetTypeChange = (event) => {
this.setState({ petType: event.target.value });
};
render() {
return (
<div>
<h2>Complex Form</h2>
{this.state.errors.length > 0 && (
<ul>
{this.state.errors.map((error) => (
<li key={error}>{error}</li>
))}
</ul>
)}
<form onSubmit={this.handleSubmit}>
<div>
<label htmlFor="name">Name:</label>
<input type="text" id="name" value={this.state.name} onChange={this.handleNameChange} />
</div>
<div>
<label htmlFor="email">Email:</label>
<input type="email" id="email" value={this.state.email} onChange={this.handleEmailChange} />
</div>
<div>
<label htmlFor="phone">Phone:</label>
<input type="tel" id="phone" value={this.state.phone} onChange={this.handlePhoneChange} />
</div>
<div>
<label htmlFor="newsletter">Subscribe to newsletter:</label>
<input type="checkbox" id="newsletter" checked={this.state.newsletter} onChange={this.handleNewsletterChange} />
</div>
<div>
<label htmlFor="hasPets">Do you have pets?</label>
<input type="checkbox" id="hasPets" checked={this.state.hasPets} onChange={this.handleHasPetsChange
Problem 9
Implement a chat application using React that allows users to send and receive messages in real-time. The application should use WebSockets to communicate with a server and update the UI in real-time as new messages are received. The UI should display a list of messages, a text input field for entering new messages, and a button for submitting messages.
Solution:
We'll start by creating a new React component called ChatApp. This component will be responsible for handling the WebSocket connection and rendering the chat UI.
JSX
import React, { useState, useEffect } from 'react';
function ChatApp() {
const [messages, setMessages] = useState([]);
const [messageInput, setMessageInput] = useState('');
const [socket, setSocket] = useState(null);
useEffect(() => {
// create a new WebSocket connection
const newSocket = new WebSocket('ws://localhost:3000');
// handle incoming messages from the server
newSocket.onmessage = (event) => {
const newMessage = JSON.parse(event.data);
setMessages([...messages, newMessage]);
};
setSocket(newSocket);
return () => {
newSocket.close();
};
}, []);
const handleSendMessage = () => {
// create a new message object
const newMessage = {
id: Date.now(),
text: messageInput,
timestamp: new Date().toISOString(),
};
// send the message to the server
socket.send(JSON.stringify(newMessage));
// clear the message input field
setMessageInput('');
};
return (
<div>
<h1>Chat App</h1>
<ul>
{messages.map((message) => (
<li key={message.id}>
{message.text} ({message.timestamp})
</li>
))}
</ul>
<div>
<input
type="text"
value={messageInput}
onChange={(event) => setMessageInput(event.target.value)}
/>
<button onClick={handleSendMessage}>Send</button>
</div>
</div>
);
}
export default ChatApp;
In this component, we first set up the initial state using useState. We have three pieces of state: messages, which is an array of messages that we will render in the UI, messageInput, which is the text input field for the user to enter new messages, and socket, which is the WebSocket connection.
Next, we use useEffect to set up the WebSocket connection. We create a new WebSocket object and handle incoming messages from the server by adding them to the messages array using setMessages. We also set the socket state using setSocket.
In the handleSendMessage function, we create a new message object using the Date and toISOString methods to generate a unique ID and timestamp for the message. We then send the message to the server using the WebSocket connection and clear the message input field using setMessageInput('').
Finally, we render the chat UI using a simple unordered list to display the messages, a text input field for entering new messages, and a button for submitting messages. When the user clicks the Send button, we call the handleSendMessage function to send the message to the server.
Note: This is a basic example of a chat application using WebSockets. In a real-world scenario, you would need to implement more advanced features such as user authentication, message encryption, and message history.
Problem 10
Build a React component that displays a scatter plot with interactive features such as zooming and panning. The component should be able to handle large datasets with up to 10,000 data points.
Solution:
To solve this problem, we can use a popular charting library such as D3.js or Highcharts. These libraries provide many built-in features for creating complex data visualizations, including scatter plots with zooming and panning.
Here's an example implementation using Highcharts:
JAVASCRIPT
import React, { useRef, useEffect } from 'react';
import Highcharts from 'highcharts';
import HighchartsReact from 'highcharts-react-official';
const ScatterPlot = ({ data }) => {
const chartRef = useRef(null);
useEffect(() => {
if (chartRef.current) {
const chart = chartRef.current.chart;
// Set the chart data
chart.update({
series: [{
type: 'scatter',
data: data,
}]
});
// Set up the zooming and panning behavior
chart.update({
chart: {
zoomType: 'xy',
panning: true,
panKey: 'ctrl',
},
});
}
}, [data]);
return (
<HighchartsReact
highcharts={Highcharts}
options={{
title: {
text: 'Scatter Plot',
},
xAxis: {
title: {
text: 'X Axis',
},
},
yAxis: {
title: {
text: 'Y Axis',
},
},
series: [{
type: 'scatter',
data: data,
}]
}}
ref={chartRef}
/>
);
};
export default ScatterPlot;
In this implementation, we first import the Highcharts library and its React wrapper, HighchartsReact. We then define a functional component called ScatterPlot that takes a data prop, which is an array of objects representing the data points for the scatter plot.
Inside the component, we create a chartRef using the useRef hook, which we will use to update the chart in the useEffect hook. Inside the useEffect hook, we update the chart with the new data and set up the zooming and panning behavior. We use the chart.update method to set the chart data and options.
Finally, we render the HighchartsReact component with the necessary options and pass in the chartRef. This will render the scatter plot with the desired features.
Overall, this implementation provides a scalable and interactive solution for displaying large datasets in a scatter plot with zooming and panning.
