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

In this example, we are going to learn how to check whether a string contains a substring or not in JavaScript?
Submitted by IncludeHelp, on February 14, 2019

Given a string, substring and we have to check whether a string contains a substring or not?

Checking string contains substring or not

There are two popular ways to check whether a substring exists in a string or not?

1) Using JavaScript includes() method

includes() method is a string method in JavaScript, it returns true if the string contains a substring or not?

Syntax:

    string.includes(substring);

JavaScript Code to check whether a string contains a substring or not using includes() method:

<script>
	var str = "Hello world!";
	var substr = "Hello";
	if(str.includes(substr)==true){
		document.write(str + " contains " + substr + "<br>");
	}
	else{
		document.write(str + " does not contain " + substr + "<br>");
	}

	substr = "Okay";
	if(str.includes(substr)==true){
		document.write(str + " contains " + substr + "<br>");
	}
	else{
		document.write(str + " does not contain " + substr + "<br>");
	}		
</script>

Output

Hello world! contains Hello
Hello world! does not contain Okay

2) Using JavaScript indexOf() method

indexOf() is a string method in JavaScript, if substring founds in the string - it returns the starting position of the substring if substring does not found in the string – it returns -1.

Syntax:

    string.indexOf(substring);

JavaScript Code to check whether a string contains a substring or not using indexOf() method:

<script>
	var str = "Hello world!";
	var substr = "Hello";
	if(str.indexOf(substr) != -1){
		document.write(str + " contains " + substr + "<br>");
	}
	else{
		document.write(str + " does not contain " + substr + "<br>");
	}

	substr = "Okay";
	if(str.indexOf(substr) != -1){
		document.write(str + " contains " + substr + "<br>");
	}
	else{
		document.write(str + " does not contain " + substr + "<br>");
	}		
</script>

Output

Hello world! contains Hello
Hello world! does not contain Okay