Map.prototype.keys()

keys() 返回一个新的 Iterator 对象。它包含按照顺序插入 Map 对象中每个元素的key值。

语法

myMap.keys()

返回值

一个新的 Map iterator 对象.

例子

使用 keys()

var myMap = new Map();
myMap.set("0", "foo");
myMap.set(1, "bar");
myMap.set({}, "baz");

var mapIter = myMap.keys();

console.log(mapIter.next().value); // "0"
console.log(mapIter.next().value); // 1
console.log(mapIter.next().value); // Object

规范

规范 状态 备注
ECMAScript 2015 (6th Edition, ECMA-262)
Map.prototype.keys		 Standard Initial definition.
ECMAScript Latest Draft (ECMA-262)
Map.prototype.keys		 Draft

浏览器兼容性

Update compatibility data on GitHub
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
keys Chrome Full support 38 Edge Full support 12 Firefox Full support 20 IE No support No Opera Full support 25 Safari Full support 8 WebView Android Full support 38 Chrome Android Full support 38 Firefox Android Full support 20 Opera Android Full support 25 Safari iOS Full support 8 Samsung Internet Android Full support 3.0 nodejs Full support 0.12

Legend

Full support  
Full support
No support  
No support

参见

  1. JavaScript 标准库
  2. Map
  3. 属性
    1. Map.prototype
    2. Map.prototype.size
    3. Map.prototype[@@toStringTag]
    4. get Map[@@species]
  4. 方法
    1. Map.prototype.clear()
    2. Map.prototype.delete()
    3. Map.prototype.entries()
    4. Map.prototype.forEach()
    5. Map.prototype.get()
    6. Map.prototype.has()
    7. Map.prototype.keys()
    8. Map.prototype.set()
    9. Map.prototype.values()
    10. Map.prototype[@@iterator]()
  5. 继承
  6. Function
  7. 属性
    1. Function.arguments
    2. Function.arity
    3. Function.caller
    4. Function.displayName
    5. Function.length
    6. Function.name
    7. Function.prototype
  8. 方法
    1. Function.prototype.apply()
    2. Function.prototype.bind()
    3. Function.prototype.call()
    4. Function.prototype.isGenerator()
    5. Function.prototype.toSource()
    6. Function.prototype.toString()
  9. Object
  10. 属性
    1. Object.prototype.__count__
    2. Object.prototype.__noSuchMethod__
    3. Object.prototype.__parent__
    4. Object.prototype.__proto__
    5. Object.prototype.constructor
  11. 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.unwatch()
    12. Object.prototype.valueOf()
    13. Object.prototype.watch()
    14. Object.setPrototypeOf()