JavaScript - How To Check Whether a String Contains a Substring?

Here are the different methods to check whether a string contains a substring in JavaScript.

1. Using includes() Method

The includes() method is the most simple and modern way to check if a string contains a specific substring. It returns true if the substring is found within the string, and false otherwise.

let s = "JavaScript is awesome!";
let res = s.includes("awesome");
console.log(res);

true

• includes() checks if the substring ("awesome") exists within the string ("JavaScript is awesome!").
• It returns a boolean value (true or false).
• This method is case-sensitive, so "awesome" is different from "Awesome".

2. Using indexOf() Method

The indexOf() method searches for a substring within a string and returns the index of the first occurrence. If the substring is not found, it returns -1.

let s = "JavaScript is awesome!";
let res = s.indexOf("awesome") !== -1; 
console.log(res);

true

• indexOf() returns the index of the first occurrence of the substring.
• If the substring is found, the result will be an index (>= 0), otherwise -1.
• You can compare the result to -1 to check if the substring is present.

3. Using Regular Expressions (RegExp)

You can also use regular expressions to check if a substring exists within a string. This is especially useful when you want to perform case-insensitive checks or match more complex patterns.

let s = "JavaScript is awesome!";
let res = /awesome/i.test(s);
console.log(res);

true

• /awesome/i.test(str) creates a regular expression to check if the word "awesome" exists in the string, ignoring case (i flag).
• The test() method returns a boolean (true or false).
• Regular expressions are more powerful but can be overkill for simple substring checks.

4. Using search() Method

The search() method allows you to search for a substring or regular expression pattern within a string. It returns the index of the first match or -1 if no match is found.

let s = "JavaScript is awesome!";
let res = s.search("awesome") !== -1;
console.log(res);

true

• search() works similarly to indexOf() but can accept regular expressions.
• If the substring is found, it returns the index, otherwise -1.
• Like indexOf(), you compare the result to -1 to check for the substring.

5. Using split() Method

The split() method splits a string into an array of substrings based on a separator. You can use it to check if the string can be split into an array that includes the substring.

let s = "JavaScript is awesome!";
let res = s.split("awesome").length > 1;
console.log(res);

true

• split("awesome") divides the string at each occurrence of "awesome".
• If the substring exists, the resulting array will have more than one element, and the length will be greater than 1.
• This method can be useful for checking multiple substrings at once.

Which Approach to Choose in Which Case?