How To Check Array Contains A Value In JavaScript

Table of Contents

3. Check Array Value Exist of Not Using Custom Method

Often developers want to check array contains a value in JavaScript. Well, there are many ways to do this. Let’s see some of the best ways to do it. Are you ready? Let’s just dive into it.

Check If a Value Exists in an Array in JavaScript

01 Use the indexOf() Method

Generally, the indexOf() method is used for both string and array. For array, you check whether a given value or element exists in an array or not. If the element found in an array then the indexOf() method returns the index of the element and returns -1 if it not found.

For string, you can check whether a given word or value exists in string or not. It will return >0 values if specified word or value found otherwise it will returns -1.

The indexOf() method is useful for older browsers and IE. Please also note that the indexOf() will not work with the IE < 9 versions.

Syntax:

array.indexOf(searchElement, startFromIndex);

Please note that indexOf() is case sensitive which means Keyboard and keyboard both are different for indexOf().

<script>

var devices = [ 'Keyboard', 'Mouse', 'Charger', 'Laptop', 'Pendrive', 'Speakers' ];

if ( devices.indexOf('Keyboard') !== -1 ) {
		
	alert('Yes, Array contains a value');
	
} else {
	
	alert('Sorry, Array does not contain a value');
	
}

</script>

02 Use the includes() Method

The includes() method will also work for both string and array the same as the indexOf() method. The only difference is in the return value. includes() will return the true if array value exists otherwise it will return with false.

Syntax:

array.includes(searchElement, startFromIndex);

Please note that includes() is also case sensitive which means Keyboard and keyboard both are different for includes().

<script>

var devices = [ 'Keyboard', 'Mouse', 'Charger', 'Laptop', 'Pendrive', 'Speakers' ];

if ( devices.includes('Keyboard') ) {
		
	alert('Yes, Array contains a value');
	
} else {
	
	alert('Sorry, Array does not contain a value');
	
}

</script>

03 Check Array Value Exist of Not Using Custom Method

Up till now, we have seen inbuilt methods of JavaScript, but what if you want to check array values existence via a user-defined method? We can easily check array values existence by using simple a loop. Let’s do it by creating a simple function and add a loop inside it.

<script>

function isInArray( arrayInput, searchElement ) {

	for ( var i = 0; i < arrayInput.length; i++ ) {
		
		if ( arrayInput[i] === searchElement ) {
			return true;
		}
	}
	
	return false;
}

var devices = [ 'Keyboard', 'Mouse', 'Charger', 'Laptop', 'Pendrive', 'Speakers' ];

var searchElement = isInArray(devices, 'Charger'); 

alert(searchElement);

</script>

The above function will take 2 arguments. The first one will be your array and the second one will be a search element. We have added === (Triple Equals) for case sensitive search you can add == (Double Equals) for case insensitive search. It will return true or false based on your inputs.

That’s it for now. We hope this article helped you to check array contains a value in JavaScript.

Additionally, read our guide:

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