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JavaScript - TypedArray indexof() Method

The JavaScript TypedArray indexOf() method is used to retrieve the first index at which the specified element is found or located. If the specified element is repeated twice in the typed array, the method will prioritize the first occurrence and return its index, not the second one.

If we specify the fromIndex parameter value to this method, it starts searching for the element from the specified fromIndex. If the element is not found between the fromIndex and the last index of the typed array, it returns −1, even if the element is present in the typed array.

Syntax

Following is the syntax of JavaScript TypedArray indexOf() method −

indexOf(searchElement, fromIndex)

Parameters

This method accepts two parameters named 'searchElement' and 'fromIndex'. The same as described below −

  • searchElement − The element to be searched.

  • fromIndex − The zero-based index(position) at which to start searching.

Return value

This method returns the first index of the searchElement.

Examples

Example 1

If we omit the fromIndex parameter and pass only the searchElement parameter to this method, it searches for this element in the entire typed array and returns the first index where the searchElement is found.

In the following program, we are using the JavaScript TypedArray indexOf() method to retrieve the first index of the specified element 2 in this typed array [1, 2, 3, 4, 5, 6, 7, 8].

<html>
<head>
   <title>JavaScript TypedArray indexof() Method</title>
</head>
<body>
   <script>
      const T_array = new Uint8Array([1, 2, 3, 4, 5, 6, 7, 8]);
      document.write("Original TypedArray: ", T_array);
      const searchElement = 3;
      document.write("<br>searchElement: ", searchElement);
      document.write("<br>The element ", searchElement, " is found at position ", T_array.indexOf(searchElement)); 
   </script>    
</body>
</html>

Output

The above program returns the first index as '2'.

Original TypedArray: 1,2,3,4,5,6,7,8
searchElement: 3
The element 3 is found at position 2

Example 2

If we pass both searchElement and fromIndex parameters to this method, it starts searching for the specified searchElement at the specified fromIndex position.

In this example of the JavaScript TypedArray indexOf() method, we are trying to retrieve the first index of the specified element 60, starting the search from the specified fromIndex position 4 in this typed array: [10, 20, 30, 40, 50, 60, 70, 80, 60].

<html>
<head>
   <title>JavaScript TypedArray indexof() Method</title>
</head>
<body>
   <script>
      const T_array = new Uint8Array([10, 20, 30, 40, 50, 60, 70, 80, 60]);
      document.write("Original TypedArray: ", T_array);
      const searchElement = 60;
      const fromIndex = 4;
      document.write("<br>searchElement: ", searchElement);
      document.write("<br>fromIndex: ", fromIndex);
      document.write("<br>The element ", searchElement, " is found at position ", T_array.indexOf(searchElement, fromIndex));
   </script>    
</body>
</html>

Output

After executing the above program, it will return the first index as 5.

Original TypedArray: 10,20,30,40,50,60,70,80,60
searchElement: 60
fromIndex: 4
The element 60 is found at position 5

Example 3

If the specified element is not present in the typed array, the indexOf() method returns -1.

In this example, we use the indexOf() method on a typed array to retrieve the first index of the element 50. However, this element is not present between the fromIndex 4 and the last index of the typed array [10, 20, 50, 30, 90, 70].

<html>
<head>
   <title>JavaScript TypedArray indexof() Method</title>
</head>
<body>
   <script>
      const T_array = new Uint8Array([10, 20, 50, 30, 90, 70]);
      document.write("Original TypedArray: ", T_array);
      const searchElement = 50;
      const fromIndex = 4;
      document.write("<br>searchElement: ", searchElement);
      document.write("<br>fromIndex: ", fromIndex);
      document.write("<br>The element ", searchElement, " is found at position ", T_array.indexOf(searchElement, fromIndex));
   </script>    
</body>
</html>

Output

Once the above program is executed, it will return -1.

Original TypedArray: 10,20,50,30,90,70
searchElement: 50
fromIndex: 4
The element 50 is found at position -1
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