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JavaScript Array lastIndexOf() Method

  • Last Updated : 01 Nov, 2021

Below is the example of the Array lastIndexOf() method.

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  • Example:




    <script>
        var name = [ 'gfg', 'cse', 'geeks', 'portal' ];
      
        a = name.lastIndexOf('gfg')
      
        // Printing result of method
        document.write(a);
    </script>
  • Output:
    0

The arr.lastIndexOf() method is used to find the index of the last occurrence of the search element provided as the argument to the function.

Syntax:

array.lastIndexOf(element, start)

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



  • element: This parameter holds the element which index will be return.
  • 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 examples illustrate the Array lastIndexOf() method in JavaScript:

  • Example 1: In this example the method will searched for the element 2 in that array return that element indesx.
    Input : [1, 2, 3, 4, 5].lastIndexOf(2);
    Output: 1
  • Example 2: In this example the method will searched for the element 9 in that array if not found then return -1.
    Input : [1, 2, 3, 4, 5].lastIndexOf(9);
    Output: -1

Code for the above method is provided below:

Program 1:




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

Output:

1

Program 2:




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

Output:

-1

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

  • Google Chrome 38 and above
  • Microsoft Edge 12 and above
  • Mozilla Firefox 28 and above
  • Safari 8 and above
  • Opera 25 and above



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