How to check whether a string contains a substring in JavaScript?

How to Check Whether a String Contains a Substring in JavaScript

In JavaScript, there are several methods to check if a string contains a substring. Here are the most commonly used methods:

1. Using includes() Method

The includes() method determines whether a string contains the characters of a specified string, returning true or false as appropriate.

Syntax:

string.includes(substring, start);

• substring: The string to search for.
• start (optional): The position in the string at which to start the search. Default is 0.

Example:

let text = "Hello, world!";
let result = text.includes("world");
console.log(result); // Output: true

2. Using indexOf() Method

The indexOf() method returns the position of the first occurrence of a specified value in a string. It returns -1 if the value is not found.

Syntax:

string.indexOf(substring, start);

• substring: The string to search for.
• start (optional): The position in the string at which to start the search. Default is 0.

Example:

let text = "Hello, world!";
let result = text.indexOf("world") !== -1;
console.log(result); // Output: true

3. Using search() Method

The search() method searches a string for a specified value or regular expression and returns the position of the match. It returns -1 if no match is found.

Syntax:

string.search(regexp);

• regexp: The regular expression to search for.

Example:

let text = "Hello, world!";
let result = text.search("world") !== -1;
console.log(result); // Output: true

4. Using Regular Expressions with test() Method

The test() method executes a search for a match between a regular expression and a specified string. It returns true or false.

Syntax:

regexp.test(string);

Example:

let text = "Hello, world!";
let pattern = /world/;
let result = pattern.test(text);
console.log(result); // Output: true

Comparison of Methods

• includes(): Simple and modern method. Best for straightforward substring checks. Introduced in ES6.
• indexOf(): Older method, works similarly but less readable than includes(). Useful for more complex checks where the position is needed.
• search(): Useful for regex searches, but less commonly used for simple substring checks.
• test(): Best for complex pattern matching using regular expressions.

Example Comparison

Here’s a quick comparison of the methods to check if a string contains the substring "world":

let text = "Hello, world!";

// Using includes()
console.log(text.includes("world")); // Output: true

// Using indexOf()
console.log(text.indexOf("world") !== -1); // Output: true

// Using search()
console.log(text.search("world") !== -1); // Output: true

// Using test() with regular expression
let pattern = /world/;
console.log(pattern.test(text)); // Output: true

Summary

To check whether a string contains a substring in JavaScript, you can use methods like includes(), indexOf(), search(), or test(). The includes() method is the most straightforward and modern way to perform this check, while the other methods offer additional flexibility for more complex searches.

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