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
• Using instanceof Operator
• Checking Constructor Property of Variable

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.

    


    

        To Check if a Variable is an Array in JavaScript
    
    

        In this article, we have used isArray()
        method to check if a variable is an array in JavaScript.
    
    Check
    


    

    

    

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.

    


    

        To Check if a Variable is an Array in JavaScript
    
    

        In this article, we have used instanceof
        operator to check if a variable is an array in JavaScript.
    
    Check
    


    

    

    

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.

    


    

        To Check if a Variable is an Array in JavaScript
    
    

        In this article, we have used constructor
        property of variable to check if a variable is an array 
        in JavaScript.
    
    Check
    


    

    

    

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.