JavaScript – Check if String contains Specified String

To check if a string str1 contains a specified string str2 in JavaScript, call includes() method on the string str1, and pass the specific string str2 as argument.

includes() method returns a boolean value. The return value is true if specified string is present in this string, or else, it returns false.

Syntax

The syntax to check if string str1 contains the string str2 is

</>
Copy
str1.includes(str2)

We can also provide an optional position index, from which the search for string str2 should happen in string str1.

The syntax to check if string str1 contains the string str2 after the position index is

</>
Copy
str1.includes(str2, index)

Examples

The following is a quick example to check if string str1 contains the string str2 in JavaScript.

</>
Copy
var str1 = 'An apple a day, keeps doctor away.';
var str2 = 'apple';
var result = str1.includes(str2);

We may use the return value of includes() method as a condition in If statement.

</>
Copy
var str1 = 'An apple a day, keeps doctor away.';
var str2 = 'apple';
if ( str1.includes(str2) ) {
    //str1 contains str2
} else {
    //str1 does not contain str2
}

In the following example, we take two strings: str1 and str2 in script, and check if string str1 contains the string str2 using includes() method. We shall display the resulting string in a div.

index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8">
</head>
<body>
    <div id="output"></div>
    <script>
        var str1 = 'An apple a day, keeps doctor away.';
        var str2 = 'apple';

        if ( str1.includes(str2) ) {
            displayOutput = 'str1 contains str2.';
        } else {
            displayOutput = 'str1 does not contain str2.';
        }
        document.getElementById('output').innerHTML = displayOutput;
    </script>
</body>
</html>

Now, let us change the value of string str2, such that string str2 is not present in the string str1.

index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8">
</head>
<body>
    <div id="output"></div>
    <script>
        var str1 = 'An apple a day, keeps doctor away.';
        var str2 = 'banana';

        if ( str1.includes(str2) ) {
            displayOutput = 'str1 contains str2.';
        } else {
            displayOutput = 'str1 does not contain str2.';
        }
        document.getElementById('output').innerHTML = displayOutput;
    </script>
</body>
</html>

The following is a quick example to check if string str1 contains the string str2 from a specific position index in JavaScript.

</>
Copy
var str1 = 'An apple a day, keeps doctor away.';
var str2 = 'apple';
var index = 8;
if ( str1.includes(str2, index) ) {
    //str1 contains str2 from specified index
} else {
    //str1 does not contain str2 from specified index
}

In the following example, we take two strings: str1 and str2 in script, and check if string str1 contains the string str2 from position 8 using includes() method.

index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8">
</head>
<body>
    <div id="output"></div>
    <script>
        var str1 = 'An apple a day, keeps doctor away.';
        var str2 = 'banana';
        var index = 8;

        if ( str1.includes(str2, index) ) {
            displayOutput = 'str1 contains str2 from specified position.';
        } else {
            displayOutput = 'str1 does not contain str2 from specified position.';
        }
        document.getElementById('output').innerHTML = displayOutput;
    </script>
</body>
</html>

Conclusion

In this JavaScript Tutorial, we learned how to check if a string contains another specific string in JavaScript, using includes() method, with examples.