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• 句法
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

has() method returns a boolean indicating whether an element with the specified key exists or not.

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

myMap.has(key)
					

参数

key

The key of the element to test for presence in the Map 对象。

返回值

true if an element with the specified key exists in the Map object; otherwise false .

范例

使用 has()

let myMap = new Map()
myMap.set('bar', "foo")
myMap.has('bar')   // returns true
myMap.has('baz')   // returns false
					

规范

规范
ECMAScript (ECMA-262) The definition of 'Map.prototype.has' 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
has	Chrome 38	Edge 12	Firefox 13	IE 11	Opera 25	Safari 8	WebView Android 38	Chrome Android 38	Firefox Android 14	Opera Android 25	Safari iOS 8	Samsung Internet Android 3.0	nodejs 0.12 0.12 0.10 Disabled Disabled From version 0.10: this feature is behind the --harmony runtime flag.

图例

完整支持

完整支持

用户必须明确启用此特征。

用户必须明确启用此特征。

另请参阅

• Map
• Map.prototype.set()
• Map.prototype.get()

元数据

• 最后修改： Jan 16, 2020

相关话题

1. 标准内置对象
2. Map
3. 特性
   1. Map.prototype.size
   2. Map.prototype[@@toStringTag]
   3. 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. 特性
   1. Function.arguments
   2. Function.caller
   3. Function.displayName
   4. Function.length
   5. Function.name
8. 方法
   1. Function.prototype.apply()
   2. Function.prototype.bind()
   3. Function.prototype.call()
   4. Function.prototype.toSource()
   5. Function.prototype.toString()
9. Object
10. 特性
    1. Object.prototype.__proto__
    2. 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.valueOf()
    12. Object.setPrototypeOf()