JavaScript Array indexOf()Method

Array 对象参考手册JavaScript Array Object

Example

Find the "Apple" element in the array:

var fruits = ["Banana", "Orange", "Apple", "Mango"]; var a = fruits.indexOf("Apple");

aResult output:

2

The output above means that the "Apple" element is located at the 3rd position in the array.

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Definition and Usage

The indexOf() method returns the position of a specified element in an array.

The method searches the array from beginning to end to see if it contains the corresponding element. The search starts at the start position in the array, or at the beginning of the array (when no start parameter is specified). If an item is found, it returns the position of the first occurrence of the item. The starting position index is 0.

If the specified element is not found in the array, -1 is returned.

TipIf you want to find the last occurrence of a string, use thelastIndexOf() method。

Browser Support

Internet ExplorerFirefoxOperaGoogle ChromeSafari

All major browsers support the indexOf() method, but Internet Explorer 8 and earlier IE versions do not support this method.

Syntax

array.indexOf(item,start)

Parameter Values

Parameter Description
item Required. The element to search for.
start Optional integer parameter. Specifies the position in the array to start the search. Its valid values are 0 to stringObject.length - 1. If this parameter is omitted, the search will start from the first character of the string.

Return Value

Type Description
Number The position of the element in the array, or -1 if it is not found.

Technical Details

JavaScript Version: 1.6

More Examples

Example

Find the "Apple" element in the array, starting the search at the fourth position of the array:

var fruits=["Banana","Orange","Apple","Mango","Banana","Orange","Apple"];
var a = fruits.indexOf("Apple",4);

aResult output:

6

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Array 对象参考手册JavaScript Array Object

Other Extensions