The slice()
method returns a shallow copy of a portion of a typed array into a new typed array object. This method has the same algorithm as Array.prototype.slice()
. TypedArray is one of the typed array types here.
Syntax
typedarray.slice([begin[, end]])
Parameters
begin
Optional- Zero-based index at which to begin extraction.
- A negative index can be used, indicating an offset from the end of the sequence.
slice(-2)
extracts the last two elements in the sequence. - If
begin
is undefined,slice
begins from index0
. end
Optional- Zero-based index before which to end extraction.
slice
extracts up to but not includingend
. - For example,
slice(1,4)
extracts the second element through the fourth element (elements indexed 1, 2, and 3). - A negative index can be used, indicating an offset from the end of the sequence.
slice(2,-1)
extracts the third element through the second-to-last element in the sequence. - If
end
is omitted,slice
extracts through the end of the sequence (typedarray.length
).
Return value
A new typed array containing the extracted elements.
Description
The slice
method does not alter. It returns a shallow copy of elements from the original typed array.
If a new element is added to either typed array, the other typed array is not affected.
Examples
Return a portion of an existing typed array
var uint8 = new Uint8Array([1,2,3]); uint8.slice(1); // Uint8Array [ 2, 3 ] uint8.slice(2); // Uint8Array [ 3 ] uint8.slice(-2); // Uint8Array [ 2, 3 ] uint8.slice(0,1); // Uint8Array [ 1 ]
Polyfill
Since there is no global object with the name TypedArray, polyfilling must be done on an "as needed" basis.
// https://tc39.github.io/ecma262/#sec-%typedarray%.prototype.slice if (!Uint8Array.prototype.slice) { Object.defineProperty(Uint8Array.prototype, 'slice', { value: Array.prototype.slice }); }
This is not a complete polyfill, since it returns an instance of Array, and not Uint8Array, so it lacks properties that would normally exist on TypedArrays.
If you need to support truly obsolete JavaScript engines that don't support Object.defineProperty
, it's best not to polyfill Array.prototype
methods at all, as you can't make them non-enumerable.
Specifications
Specification | Status | Comment |
---|---|---|
ECMAScript 2015 (6th Edition, ECMA-262) The definition of '%TypedArray%.prototype.slice' in that specification. |
Standard | Initial definition. |
ECMAScript Latest Draft (ECMA-262) The definition of '%TypedArray%.prototype.slice' in that specification. |
Living Standard |
Browser compatibility
Feature | Chrome | Edge | Firefox | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|---|
Basic support | 45 | ? | 38 | No | ? | ? |
Feature | Android webview | Chrome for Android | Edge mobile | Firefox for Android | IE mobile | Opera Android | iOS Safari |
---|---|---|---|---|---|---|---|
Basic support | ? | ? | ? | 38 | No | ? | ? |