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JavaScript Array indexOf() Method

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The JavaScript Array 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




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


Output: 

0

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

javascript




// Taking input as an array A
// having some elements.
let 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.
console.log(a);


Output: 

1

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

javascript




// Taking input as an array A
// having some elements.
let 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);


Output: 

-1

We have a complete list of Javascript Array methods, to check those please go through this Javascript Array Complete reference article.

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

We have a Cheat Sheet on Javascript where we covered all the important topics of Javascript to check those please go through Javascript Cheat Sheet-A Basic guide to JavaScript.


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Last Updated : 18 May, 2023
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