String extensions

In JavaScript, the startsWith(), endsWith(), and includes() methods are string extension methods introduced in ES6 (ECMAScript 2015) that provide convenient ways to check the beginning, end, or presence of a substring within a string. Here's an explanation of each method with code examples:

startsWith():

The startsWith() method checks whether a string starts with the characters of a specified string, returning true or false.

const str = 'Hello, world!';

console.log(str.startsWith('Hello')); // Output: true
console.log(str.startsWith('world')); // Output: false

endsWith():

The endsWith() method checks whether a string ends with the characters of a specified string, returning true or false.

const str = 'Hello, world!';

console.log(str.endsWith('world!')); // Output: true
console.log(str.endsWith('Hello'));  // Output: false

includes():

The includes() method checks whether a string contains the specified substring, returning true or false.

const str = 'Hello, world!';

console.log(str.includes('world')); // Output: true
console.log(str.includes('universe')); // Output: false

Code Example:

const str = 'Hello, world!';

// Check if the string starts with 'Hello'
console.log(str.startsWith('Hello')); // Output: true

// Check if the string ends with 'world!'
console.log(str.endsWith('world!')); // Output: true

// Check if the string includes 'world'
console.log(str.includes('world'));  // Output: true

These methods provide a convenient and efficient way to perform common string operations, such as checking for substrings or prefixes/suffixes, without needing to resort to manual string manipulation or regular expressions. They are widely supported in modern JavaScript environments and are useful for a variety of string-related tasks.