How to Check If a String Contains Another Substring in JavaScript

Checking whether a string contains another string or not is very common in JavaScript and as well as in other programming languages. Several methods are used to check if a string contains another substring in Javascript. Let's discuss one of the most common tasks bellow.

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String.includes()

This String.includes() method searches the sequence of characters in the string and returns true if a sequence of char value exists, otherwise returns false:

Javascript String.includes method searches the sequence of characters in the string
const string = "W3Docs"; const substring = "W3"; console.log(string.includes(substring));

String.indexOf

The indexOf() method returns the position of the given value's first occurrence in a string. The method tests whether there is a substring or not. If there is present, it will return the starting index of the substring; if not, it will return -1:

Javascript string.indexOf method returns the position of the value's first occurrence in a string
let string = "W3Docs"; let substring = "Docs"; console.log(string.indexOf(substring));
Both the string.includes() and string.indexof() methods are case sensitive.

Regex

RegExp provides more flexibility. To check for substrings in a string with regex can be done with the test() method of regular expression. This method is much easier to use as it returns a boolean. It returns direct true or false results compared to the indexOf() method, therefore, be a good alternative:

Javascript test method check for substrings in a string with regex
let str = 'stackabuse'; console.log(/stack/.test(str));

The test() method searches for a match between a RegExp and a specified string, thus returning true if the string is present; otherwise, it returns false.