Array.prototype.splice()

Summary

The splice() method changes the content of an array, adding new elements while removing old elements.

Syntax

array.splice(index, howMany[, element1[, ...[, elementN]]])
array.splice(index) // SpiderMonkey/Firefox extension, in this case howMany=array.length-index

Parameters

index

Index at which to start changing the array. If greater than the length of the array, actual starting index will be set to the length of the array. If negative, will begin that many elements from the end.

howMany

An integer indicating the number of old array elements to remove. If howMany is 0, no elements are removed. In this case, you should specify at least one new element. If howMany is greater than the number of elements left in the array starting at index, then all of the elements through the end of the array will be deleted. If no howMany parameter is specified (second syntax above, which is a SpiderMonkey extension), all elements after index are removed.

elementN

The elements to add to the array. If you don't specify any elements, splice simply removes elements from the array.

Returns

An array containing the removed elements. If only one element is removed, an array of one element is returned. If no elements are removed, an empty array is returned.

Description

If you specify a different number of elements to insert than the number you're removing, the array will have a different length at the end of the call.

Examples

Example: Using splice

The following script illustrate the use of splice:

var myFish = ['angel', 'clown', 'mandarin', 'surgeon'];

// removes 0 elements from index 2, and inserts 'drum'
var removed = myFish.splice(2, 0, 'drum');
// myFish is ['angel', 'clown', 'drum', 'mandarin', 'surgeon']
// removed is [], no elements removed

// removes 1 element from index 3
removed = myFish.splice(3, 1);
// myFish is ['angel', 'clown', 'drum', 'surgeon']
// removed is ['mandarin']

// removes 1 element from index 2, and inserts 'trumpet'
removed = myFish.splice(2, 1, 'trumpet');
// myFish is ['angel', 'clown', 'trumpet', 'surgeon']
// removed is ['drum']

// removes 2 elements from index 0, and inserts 'parrot', 'anemone' and 'blue'
removed = myFish.splice(0, 2, 'parrot', 'anemone', 'blue');
// myFish is ['parrot', 'anemone', 'blue', 'trumpet', 'surgeon']
// removed is ['angel', 'clown']

// removes 2 elements from index 3
removed = myFish.splice(3, Number.MAX_VALUE);
// myFish is ['parrot', 'anemone', 'blue']
// removed is ['trumpet', 'surgeon']

Specifications

Browser compatibility

Backward compatibility

In JavaScript 1.2 the splice method returns the element removed, if only one element is removed (howMany parameter is 1); otherwise, the method returns an array containing the removed elements. Note that the last browser to use JavaScript 1.2 was Netscape Navigator 4, so you can depend on splice always returning an array.

See also

• push / pop — add/remove elements from the end of the array
• unshift / shift — add/remove elements from the beginning of the array
• concat — returns a new array comprised of this array joined with other array(s) and/or value(s)