How to check If string contains a substring in javascript – A Definitive guide

Published on: | Last updated on: January 4, 2023 | By:

Javascript strings are used to represent and manipulate a sequence of characters.

You can check if string contains a substring in javascript using the string.includes(substring) method.

Basic Example

string.includes(substring);

In this tutorial, you will learn the different methods to check If a string contains a substring in JavaScript.

Using Includes() Method

Includes() method checks if the Substring is available in the String or not.

It returns

  • True – If the substring is available
  • False – If the substring is not available

includes() method is case sensitive. So, sub and Sub are different.

Use this method when you want to check if the substring exists or not and return a boolean flag as a result.

Syntax

The following syntax shows how to use the includes() method.

string.includes(substring);

Code

let str = 'substring';

let substr = 'sub';

alert(str.includes(substr));

Output

true

Code

let str = 'substring';

let substr = 'Sub';

alert(str.includes(substr));

Output

false

Check if string contains substring in case insensitive Way

You can check if a String Contains a Substring in a case insensitive way by converting both the string and the substring to either upper or lower case.

Code

The following code demonstrates converts both the string to lowercase and checks if a string contains a substring.

str.toLowerCase().includes('substr'.toLowerCase());

Using Includes with Position

includes() method also accepts start_value parameter to mention from where the search should begin.

It’s an optional parameter.

Syntax

string.includes(substring, start_index);

Code

let str = 'Search for sub in the string';

let substr = 'sub';

alert(str.includes(substr,15));

Output

The code returns the output False as the substring 'sub' is not found in the given string after the position 15.

false

Using includes() with if….else

You can use the includes method with the if...else statement if you want to perform different operations based on the existence of the substring.

Code

The following code shows how to use includes() method with if...else statement.

//the following two statements receives input from the user
let str = prompt('Enter a string');

let substr = prompt('Enter the substring that you want to check');

//the following statements performs the comparison
if(str.includes(substr)){

console.log(`The given string contains the substring ${substr}`);
}

else{

console.log(`The given string does not contain the substring ${substr}`);
}

Output

Enter a string: substring

Enter the substring that you want to check: sub

The given string contains the substring sub

Using indexOf() method

If you want to know the position of first occurrence of the substring in a given string, you can use the indexOf() method.

Returns

  • Index_position – If the string is present
  • -1 – If the Substring is not present

Like includes() method, indexOf() method is also case sensitive.

Use this method when you want to check if a substring exists in a string and return the index position as a result.

Syntax

string.indexOf(substring);

Code

let str = 'jsowl';

let substr = 'owl';

alert(str.indexOf(substr));

Output

   2

Code

The following code demonstrates the return value when the substring is not available.

let str = 'stackvidhya';

alert(str.indexOf('sub'));

Output

-1

Using indexof With Position

In the indexof() method, you can specify the position from where the search should begin using the offset_parameter.

It is an optional parameter.

Syntax

string.indexOf(substring,offset_parameter);

Code

let str = 'stackvidhya';

alert(str.indexOf('vid',2));

Output

5

Using Search() Method

search() method checks the presence of a particular substring in the given string.

It returns the first position of the match even if more matches are found.

  • Index_position – If the string is present
  • -1 – If the Substring is not present

Use this method when you want to use a regular expression to check if a substring match is available in the string and return an index position.

Syntax

string.search('substring');

Code

let str =  "search method is used here to check the presence of substring";

alert(str.search('sub')  !==  -1);

Output

true

Code

let str =  "search method is used here to check the presence of substring";

alert(str.search('Sub')  !==  -1);

Output

false

Using Match() Method

match() is another method that checks the presence of a substring in the given string.

  • It accepts a regular expression as a parameter to perform the match.
  • Returns an array of all matches found in the string.

Use this method when you want to use a regular expression to check if a substring match is available in the string and return an array of all matches.

Syntax

string.match(substring);

Code

let str = 'the match method takes regular expression as the parameter';

alert(str.match(/match/)!==null);

alert(str.match(/The/i)!==null); //i is a case insensitive modifier to make the search case insensitive

Output

true

true

Using Regex Test() Method

test() method is used to check for the substring in the given string.

  • It creates a regular expression for the substring
  • Compares the regex against the given string.

It returns

  • True in case if the match is found
  • false if match is not found.

Use the test() method when you want to check if a substring exists in a string using a regular expression and return True or False.

Syntax

regex.test(string);

Code

let str = 'The string contains regex';

let substr = /Regex/i; ////i is a case insensitive modifier to make the search case

substr.test(str);

Output

true

JSfiddle

This tutorial is available in this JSFiddle.

Additional Resources

Leave a Comment