How to check object is an array in JavaScript? - GeeksforGeeks

25 Apr, 2019
Method 1: Using Array.isArray() function: The Array.isArray() function determines whether the value passed to this function is an array or not. This function returns true if the argument passed is array else it returns false.
Syntax:
Array.isArray(obj)
Here, obj is any valid object in JavaScript like map, list, array, string, etc.
Return Value: It returns Boolean value true if the object passed is an array or false if the object passed is not an array.
Example 1: This example uses Array.isArray() function to check the object is array or not.
<!DOCTYPE html><html>  <head>    <title>        check object is an array    </title></head>  <body>    <p>        Click on button to        check for array    </p>          <button onclick="myFunction()">        Try it    </button>          <p id="GFG"></p>          <script>        function myFunction() {            var countries = ["India", "USA", "Canada"];            var x = document.getElementById("GFG");            x.innerHTML = Array.isArray(countries);        }    </script></body>  </html>                    
Output:
Example 2: This example uses Array.isArray() function to check the object is array or not.
<!DOCTYPE html><html>  <head>    <title>        check object is an array    </title></head>  <body>    <p>        Click on button to        check for array    </p>          <button onclick="myFunction()">        Try it    </button>          <p id="GFG"></p>          <script>        function myFunction() {                           // It returns false as the object passed is            // String not an array            document.write(Array.isArray(                    'hello GeeksForGeeks'));        }     </script></body>  </html>                    
Output:
Before Clicking the button:
After Clicking the button:
Example 3: This example uses Array.isArray() function to check the object is array or not.
<!DOCTYPE html><html>  <head>    <title>        check object is an array    </title></head>  <body>    <p>        Click on button to        check for array    </p>          <button onclick="myFunction()">        Try it    </button>          <p id="GFG"></p>          <script>        function myFunction() {                           // It returns false as the object passed is            // String not an array            document.write(Array.isArray({k:12}));        }     </script></body>  </html>                    
Output:
Before Clicking the button:
After Clicking the button:
Method 2: Using typeof operator: In JavaScript, the typeof operator returns the data type of its operand in the form of a string where an operand can be any object, function or variable. However, the problem with this is that it isn’t applicable for determining array.
Syntax:
typeof operand or typeof(operand)
Example:
<!DOCTYPE html><html>  <head>    <title>        check object is an array    </title></head>  <body>    <p id="GFG"></p>           <script>         document.getElementById("GFG").innerHTML          = typeof "Geeks" + "<br>" +             typeof [1, 2, 3, 4] + "<br>" +             typeof {name:'Kartik', age:20} + "<br>" +             typeof new Date() + "<br>" +             typeof function () {} + "<br>" +             typeof job + "<br>" +             typeof null;     </script> </body>   </html>                    
Output:
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