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

JavaScript provides us with different methods to check whether a string contains a substring or not. In this article, we use the following three methods for this purpose:

• String search() method

• String indexOf() method

• String includes() method

Let's explore in detail each method.

Using String search() Method

The string search() method can be used to search a text (using regular expression) in a string. It matches the string against a regular expression and returns the index (position) of the first match. It returns -1 if no match is found. It's case-sensitive.

The string search() method is an ES1 feature and is fully supported in all browsers.

Syntax

string.search(searchValue)

searchValue is a regular expression or a string (will be converted to a regular expression).

Example

You can try to run the following code to check whether the string "Tutorialspoint: Free Video Tutorial" contains a substring "point" or not using the search() method:

var re = "point";
var str = "Tutorialspoint: Free Video Tutorials";

if (str.search(re) == -1) {
    document.write("Does not contain Point");
} else {
    document.write("Contains Point!");
}

Contains Point!

Using String indexOf() Method

The string indexOf() method can be used to check if a string contains a substring or not. It returns the position of the first occurrence of a value (substring) in the string, otherwise it returns -1 if the value is not found.

The string indexOf() method is case-sensitive and cannot search against a regular expression. It is an ES1 feature and is fully supported in all browsers.

Syntax

string.indexOf(searchvalue, start)

Parameters

searchValue - is a string to search for.

start - the index to start from (default is 0). It's an optional parameter.

Example

In the example program below, we use string indexOf() method to check whether the string "Tutorialspoint: Free Video Tutorial" contains a substring "point" or not:

var re = "point";
var str = "Tutorialspoint: Free Video Tutorials";

if (str.indexOf(re) !== -1) {
    document.write("Contains " + re);
} else {
    document.write("Does not contain " + re);
}

Contains point

Using String includes() Method

The string includes() method is introduced in ES6 and is supported in all modern browsers. It returns true if a string contains a specified substring, otherwise it returns false.

The includes() method is case sensitive. This method is not supported in Internet Explorer 11 (or earlier).

Syntax

string.includes(searchvalue, start)

Parameters

searchValue - is a string to search for.

start - the index to start from (default is 0). It's an optional parameter.

Example

In the example program below, we use the string includes() method to check whether the string "Tutorialspoint: Simply Easy Learning" contains a substring "JavaScript" or not:

var re = "JavaScript";
var str = "Tutorialspoint: Simply Easy Learning";

if (str.includes(re)) {
    document.write("Contains " + re);
} else {
    document.write("Does not contain " + re);
}

Does not contain JavaScript

Comparison

Conclusion

For simple substring checking, use includes() for cleaner boolean results. Use indexOf() for older browser compatibility, and search() when you need regex pattern matching.