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JavaScript Array indexOf() Method

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  • Last Updated : 13 Oct, 2022
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The arr.indexOf() method is used to find the index of the first occurrence of the search element provided as the argument to the method. 

Syntax: 

array.indexOf(element, start)

Parameters: This method accepts two parameters as mentioned above and described below: 

  • element: This parameter holds the element whose index will be returned.
  • start: This parameter is optional and it holds the starting point of the array, where to begin the search the default value is 0.

Return value: This method returns the index of the first occurrence of the element. If the element cannot be found in the array, then this method returns -1.

Below is an example of the Array indexOf() method. 

Example 1: 

javascript




<script>
    var name = [ 'gfg', 'cse', 'geeks', 'portal' ];
    a = name.indexOf('gfg')
    // Printing result of method
    console.log(a);
</script>

Output: 

0

Example 2: In this example, the method will be searched for element 2 in that array and return that element index. 

Input : [1, 2, 3, 4, 5].indexOf(2);
Output: 1

Example 3: In this example, the method will be searched for element 9 in that array if not found then return -1. 

Input : [1, 2, 3, 4, 5].indexOf(9);
Output: -1

Code for the above method is provided below

Program 1: 

javascript




<script>
    // Taking input as an array A
    // having some elements.
    var A = [ 1, 2, 3, 4, 5 ];
    // indexOf() method is called to
    // test whether the searching element
    // is present in given array or not.
    a = A.indexOf(2)
    // Printing result of method.
    document.write(a);
</script>

Output: 

1

Program 2: 

javascript




<script>
    // Taking input as an array A
    // having some elements.
    var name = [ 'gfg', 'cse', 'geeks', 'portal' ];
    // indexOf() method is called to
    // test whether the searching element
    // is present in given array or not.
    a = name.indexOf('cat')
    // Printing result of method
    console.log(a);
</script>

Output: 

-1

Supported Browsers: The browsers supported by JavaScript Array indexOf() method are listed below: 

  • Google Chrome 1 and above
  • Edge 12 and above
  • Firefox 1.5 and above
  • Internet Explorer 9 and above
  • Opera 9.5 and above
  • Safari 3 and above

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