Popular Libraries

JavaScript libraries are collections of pre-written code that provide specific functionalities and utilities to simplify common programming tasks. Some popular JavaScript libraries include:

React

React is a popular JavaScript library for building user interfaces developed and maintained by Facebook. It follows a component-based architecture and makes use of a virtual DOM for efficient rendering.

import React from 'react';
import ReactDOM from 'react-dom';
function HelloWorld() {
return (
<div>Hello, World!</div>
);
}
ReactDOM.render(, document.getElementById('root'));

Angular

Angular is a comprehensive framework developed and maintained by Google for building web applications. It provides a structured approach to building single-page applications (SPAs) and offers features like dependency injection, routing, and powerful templates.

import { Component } from '@angular/core';
@Component({
selector: 'app-root',
template:     <h1>Hello, {{ name }}!</h1>  
})
export class AppComponent {
name = 'Angular';
}

Vue.js

Vue.js is a progressive JavaScript framework for building user interfaces. It is designed to be incrementally adoptable, allowing developers to integrate it into existing projects or build new applications from scratch.

<script>
import Vue from 'vue'
import App from './App.vue'
new Vue({
el: '#app',
render: h => h(App)
})

JavaScript Testing Frameworks

Testing frameworks help developers write and run automated tests for their JavaScript code, ensuring its correctness and reliability.

Jest

Jest is a popular testing framework developed and used by Facebook. It provides a comprehensive set of features for writing and running tests, including code coverage, snapshot testing, and parallel test execution.

// sum.test.js
const sum = require('./sum');
test('adds 1 + 2 to equal 3', () => {
expect(sum(1, 2)).toBe(3);
});

Mocha

Mocha is a feature-rich JavaScript test framework running on Node.js and in the browser. It provides a flexible and extensible approach to testing, allowing developers to choose their preferred assertion library and reporting style.

const assert = require('assert');
describe('Array', function() {
describe('#indexOf()', function() {
it('should return -1 when the value is not present', function() {
assert.equal([1, 2, 3].indexOf(4), -1);
});
});
});

Jasmine

Jasmine is a behavior-driven development framework for testing JavaScript code. It provides a clean and straightforward syntax for writing tests and supports features like spies, asynchronous testing, and custom matchers.

describe('Calculator', () => {
let calculator;
beforeEach(() => {
calculator = new Calculator();
});
it('should add two numbers', () => {
expect(calculator.add(2, 3)).toBe(5);
});
});

In the final chapter, we'll explore some advanced topics in JavaScript, such as asynchronous programming, regular expressions, functional programming, and performance optimization.