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How to Check if a Variable is an Array in JavaScript?
To check if a variable is an array in Javascript is essential to handle data appropriately. We will discuss three different approaches to check if a variable is an array or not.
We are having an array and a string, and our task is to check if a variable is an array in JavaScript.
Approaches to Check if a Variable is an Array
Here is a list of approaches to check if a variable is an array in JavaScript which we will be discussing in this article with stepwise explaination and complete example codes.
Using isArray() Method
To check if a variable is an array in JavaScript, we have used isArray() method. It returns a boolean value as result, either true or false.
- We have used two div elements to display the array and output using getElementById() and innerHTML property. We have also added a button which triggers checkArray() function upon clicking.
- We have initialized and stored an array in arr and a string in variable str.
- Then we have used isArray() method on both, array and string and stored this result in res1 and res2 respectively.
Example
Here is a complete example code implementing above mentioned steps to check if a variable is an array in JavaScript using isArray() method.
<!DOCTYPE html>
<html lang="en">
<head>
<title>
To Check if a Variable is an Array in JavaScript
</title>
</head>
<body>
<h2>
To Check if a Variable is an Array in JavaScript
</h2>
<p>
In this article, we have used <strong>isArray()</strong>
method to check if a variable is an array in JavaScript.
</p>
<button onclick="checkArray()">Check</button>
<br><br>
<div id="array"></div>
<div id="result"></div>
<script>
let arr = [1, 2, 3, 4, 5];
let str = "Tutorialspoint";
document.getElementById('array')
.innerHTML= "Variable: " +arr +"<br>"
+"Variable: " +str;
function checkArray() {
let res1 = Array.isArray(arr);
let res2 = Array.isArray(str);
document.getElementById("result")
.innerHTML = "Is it array?: " +"<br>" +res1
+"<br>" +res2;
}
</script>
</body>
</html>
Using instanceof Operator
In this approach we have used instanceof Array operator to check if a variable is an array in JavaScript.
- We have used two div elements to display the array and output using getElementById() and innerHTML property. We have also added a button which triggers checkArray() function upon clicking.
- We have initialized and stored an array in arr and a string in variable str.
- Then we have used instanceof Array operator on both, array and string and stored this result in res1 and res2 respectively.
Example
Here is a complete example code implementing above mentioned steps to check if a variable is an array in JavaScript using instanceof operator.
<!DOCTYPE html>
<html lang="en">
<head>
<title>
To Check if a Variable is an Array in JavaScript
</title>
</head>
<body>
<h2>
To Check if a Variable is an Array in JavaScript
</h2>
<p>
In this article, we have used <strong>instanceof</strong>
operator to check if a variable is an array in JavaScript.
</p>
<button onclick="checkArray()">Check</button>
<br><br>
<div id="array"></div>
<div id="result"></div>
<script>
let arr = [1, 2, 3, 4, 5];
let str = "Tutorialspoint";
document.getElementById('array')
.innerHTML= "Variable: " +arr +"<br>"
+"Variable: " +str;
function checkArray() {
let res1 = arr instanceof Array;
let res2 = str instanceof Array;
document.getElementById("result")
.innerHTML = "Is it array?: " +"<br>" +res1
+"<br>" +res2;
}
</script>
</body>
</html>
Checking constructor Property of Variable
In this approach to check if a variable is an array in JavaScript we have checked constructor property of variable.
- We have used two div elements to display the array and output using getElementById() and innerHTML property. We have also added a button which triggers checkArray() function upon clicking.
- We have initialized and stored an array in arr and a string in variable str.
- Then we have checked the constructor property of array and string using arr.constructor === Array and str.constructor === Array; and stored this result in res1 and res2 respectively.
Example
Here is a complete example code implementing above mentioned steps to check if a variable is an array in JavaScript by checking constructor property of variable. It displays true when the variable is same as what we specified.
<!DOCTYPE html>
<html lang="en">
<head>
<title>
To Check if a Variable is an Array in JavaScript
</title>
</head>
<body>
<h2>
To Check if a Variable is an Array in JavaScript
</h2>
<p>
In this article, we have used <strong>constructor</strong>
property of variable to check if a variable is an array
in JavaScript.
</p>
<button onclick="checkArray()">Check</button>
<br><br>
<div id="array"></div>
<div id="result"></div>
<script>
let arr = [1, 2, 3, 4, 5];
let str = "Tutorialspoint";
document.getElementById('array')
.innerHTML= "Variable: " +arr +"<br>"
+"Variable: " +str;
function checkArray() {
let res1 = arr.constructor === Array;
let res2 = str.constructor === Array;
document.getElementById("result")
.innerHTML = "Is it array?: " +"<br>" +res1
+"<br>" +res2;
}
</script>
</body>
</html>
Conclusion
In this article we discussed how check if a variable is an array in JavaScript using three different approaches which are: by using isArray() method, instanceof operator and by checking constructor property of variable.
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