JavaScript String includes() Method - GeeksforGeeks

07 Oct, 2021
Below is the example of the String includes() Method.  
Example:  
javascript
<!DOCTYPE html><html>    <body>        <p id="GFG"></p>         <script>            var str = "Welcome to GeeksforGeeks.";            var check = str.includes("Geeks");            document.getElementById("GFG").innerHTML = check;        </script>    </body></html>
Output: 
true
In JavaScript, includes() method determines whether a string contains the given characters within it or not. This method returns true if the string contains the characters, otherwise, it returns false. Note: The includes() method is case sensitive i.e, it will treat the Uppercase characters and Lowercase characters differently.Syntax:  
string.includes(searchvalue, start)
Parameters Used:  
search value: It is the string in which the search will take place.
start: This is the position from where the search will be processed (although this parameter is not necessary if this is not mentioned the search will begin from the start of the string).
Returns either a Boolean true indicating the presence or it returns a false indicating the absence.
Examples:  
Input : Welcome to GeeksforGeeks.
        str.includes("Geeks");


Output : true
Explanation: Since the second parameter is not defined, the search will take place from the starting index. And it will search for Geeks, as it is present in the string, it will return a true. 
Input: Welcome to GeeksforGeeks.


Output: false
Explanation: Even in this case the second parameter is not defined, so the search will take place from the starting index. But as this method is case sensitive it will treat the two strings differently, hence returning a boolean false. Since it is case sensitive. Codes for the above function are provided below.Code 1:  
javascript
<!DOCTYPE html><html>    <body>        <p id="GFG"></p>         <script>            var str = "Welcome to GeeksforGeeks.";            var check = str.includes("Geeks");            document.getElementById("GFG").innerHTML = check;        </script>    </body></html>
Output:  
false
Code 2:  
javascript
<!DOCTYPE html><html>    <body>        <p id="GFG"></p>         <script>            var str = "Welcome to GeeksforGeeks.";            var check = str.includes("geeks");            document.getElementById("GFG").innerHTML = check;        </script>    </body></html>
Output:  
false
Code 3:  
javascript
<!DOCTYPE html><html>    <body>        <p id="GFG"></p>         <script>            var str = "Welcome to GeeksforGeeks.";            var check = str.includes("o", 17);            document.getElementById("GFG").innerHTML = check;        </script>    </body></html>
Output:  
true
Code 4:  
javascript
<!DOCTYPE html><html>    <body>        <p id="GFG"></p>         <script>            var str = "Welcome to GeeksforGeeks.";            var check = str.includes("o", 18);            document.getElementById("GFG").innerHTML = check;        </script>    </body></html>
Output:  
false
Exceptions :  
The search will not be processed if the second parameter i.e computed index(starting index) is greater than or equal to the string length and hence return false.  
javascript
<!DOCTYPE html><html>    <body>        <p id="GFG"></p>         <script>            var str = "Welcome to GeeksforGeeks.";            var check = str.includes("o", 25);            document.getElementById("GFG").innerHTML = check;        </script>    </body></html>
Output:  
false
 
If the computed index(starting index) i.e the position from which the search will begin is less than 0, the entire array will be searched.  
javascript
<!DOCTYPE html><html>    <body>        <p id="GFG"></p>         <script>            var str = "Welcome to GeeksforGeeks.";            var check = str.includes("o", -2);            document.getElementById("GFG").innerHTML = check;        </script>    </body></html>
Output:  
true
 
Supported Browser:
Chrome 41 and above
Edge 12 and above
Firefox 40 and above
Opera 28 and above
Safari 9 and above
JavaScript is best known for web page development but it is also used in a variety of non-browser environments. You can learn JavaScript from the ground up by following this JavaScript Tutorial and JavaScript Examples.
 
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JavaScript
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