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• 句法
• 描述
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

map() method creates a new typed array with the results of calling a provided function on every element in this typed array. This method has the same algorithm as Array.prototype.map() . TypedArray is one of the typed array types here.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

句法

typedArray.map(mapFn[, thisArg])
					

参数

mapFn

A callback function that produces an element of the new typed array, taking three arguments:

currentValue

The current element being processed in the typed array.

index 可选

The index of the current element being processed in the typed array.

array 可选

The typed array map() was called upon.

thisArg 可选

Value to use as this when executing mapFn .

返回值

A new typed array.

描述

map() method calls a provided callback function ( mapFn ) once for each element in a typed array, in order, and constructs a new typed array from the results.

mapFn is invoked only for indexes of the typed array which have assigned values; it is not invoked for indexes that are undefined , those which have been deleted, or which have never been assigned values.

mapFn is invoked with three arguments: the value of the element, the index of the element, and the typed array object being traversed.

若 thisArg parameter is provided to map() , it will be passed to mapFn when invoked, for use as its this value. Otherwise, the value undefined will be passed for use as its this value. The this value ultimately observable by mapFn is determined according to the usual rules for determining the this seen by a function .

map() does not mutate the typed array on which it is called (although mapFn , if invoked, may do so).

The range of elements processed by map() is set before the first invocation of mapFn . Elements which are appended to the array after the call to map() begins will not be visited by mapFn . If existing elements of the typed array are changed, or deleted, their value as passed to mapFn will be the value at the time map() visits them; elements that are deleted are not visited.

范例

Mapping a typed array to a typed array of square roots

The following code takes a typed array and creates a new typed array containing the square roots of the numbers in the first typed array.

const numbers = new Uint8Array([1, 4, 9]);
const roots = numbers.map(Math.sqrt);
// roots is now: Uint8Array [1, 2, 3],
// numbers is still Uint8Array [1, 4, 9]
					

Mapping a typed array of numbers using a function containing an argument

The following code shows how map works when a function requiring one argument is used with it. The argument will automatically be assigned to each element of the typed array as map loops through the original typed array.

const numbers = new Uint8Array([1, 4, 9]);
const doubles = numbers.map(function(num) {
  return num * 2;
});
// doubles is now Uint8Array [2, 8, 18]
// numbers is still Uint8Array [1, 4, 9]
					

规范

规范
ECMAScript (ECMA-262) The definition of 'TypedArray.prototype.map' in that specification.

浏览器兼容性

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
map	Chrome 45	Edge 14	Firefox 38	IE No	Opera 32	Safari No	WebView Android 45	Chrome Android 45	Firefox Android 38	Opera Android 32	Safari iOS No	Samsung Internet Android 5.0	nodejs 4.0.0

图例

完整支持

完整支持

不支持

不支持

另请参阅

• TypedArray.prototype.filter()
• Array.prototype.map()

元数据

• 最后修改： 2020 年 1 月 22 日

相关话题

1. 标准内置对象
2. TypedArray
3. 特性
   1. TypedArray.BYTES_PER_ELEMENT
   2. TypedArray.name
   3. TypedArray.prototype.buffer
   4. TypedArray.prototype.byteLength
   5. TypedArray.prototype.byteOffset
   6. TypedArray.prototype.length
   7. get TypedArray[@@species]
4. 方法
   1. TypedArray.from()
   2. TypedArray.of()
   3. TypedArray.prototype.copyWithin()
   4. TypedArray.prototype.entries()
   5. TypedArray.prototype.every()
   6. TypedArray.prototype.fill()
   7. TypedArray.prototype.filter()
   8. TypedArray.prototype.find()
   9. TypedArray.prototype.findIndex()
   10. TypedArray.prototype.forEach()
   11. TypedArray.prototype.includes()
   12. TypedArray.prototype.indexOf()
   13. TypedArray.prototype.join()
   14. TypedArray.prototype.keys()
   15. TypedArray.prototype.lastIndexOf()
   16. TypedArray.prototype.map()
   17. TypedArray.prototype.reduce()
   18. TypedArray.prototype.reduceRight()
   19. TypedArray.prototype.reverse()
   20. TypedArray.prototype.set()
   21. TypedArray.prototype.slice()
   22. TypedArray.prototype.some()
   23. TypedArray.prototype.sort()
   24. TypedArray.prototype.subarray()
   25. TypedArray.prototype.toLocaleString()
   26. TypedArray.prototype.toString()
   27. TypedArray.prototype.values()
   28. TypedArray.prototype[@@iterator]()
5. 相关页面：
6. Int8Array
7. Uint8Array
8. Uint8ClampedArray
9. Int16Array
10. Uint16Array
11. Int32Array
12. Uint32Array
13. Float32Array
14. Float64Array
15. BigInt64Array
16. BigUint64Array
17. 继承：
18. Function
19. 特性
    1. Function.arguments
    2. Function.caller
    3. Function.displayName
    4. Function.length
    5. Function.name
20. 方法
    1. Function.prototype.apply()
    2. Function.prototype.bind()
    3. Function.prototype.call()
    4. Function.prototype.toSource()
    5. Function.prototype.toString()
21. Object
22. 特性
    1. Object.prototype.__proto__
    2. Object.prototype.constructor
23. 方法
    1. Object.prototype.__defineGetter__()
    2. Object.prototype.__defineSetter__()
    3. Object.prototype.__lookupGetter__()
    4. Object.prototype.__lookupSetter__()
    5. Object.prototype.hasOwnProperty()
    6. Object.prototype.isPrototypeOf()
    7. Object.prototype.propertyIsEnumerable()
    8. Object.prototype.toLocaleString()
    9. Object.prototype.toSource()
    10. Object.prototype.toString()
    11. Object.prototype.valueOf()
    12. Object.setPrototypeOf()