在此页

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

静态 Reflect .isExtensible() method determines if an object is extensible (whether it can have new properties added to it). It is similar to Object.isExtensible() , but with some differences .

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

Reflect.isExtensible(target)
					

参数

target

The target object which to check if it is extensible.

返回值

A 布尔 indicating whether or not the target is extensible.

异常

A TypeError , if target is not an Object .

描述

Reflect.isExtensible method allows you determine if an object is extensible (whether it can have new properties added to it). It is the same method as Object.isExtensible() .

范例

使用 Reflect.isExtensible()

另请参阅 Object.isExtensible() .

// New objects are extensible.
let empty = {}
Reflect.isExtensible(empty)  // === true
// ...but that can be changed.
Reflect.preventExtensions(empty)
Reflect.isExtensible(empty)  // === false
// Sealed objects are by definition non-extensible.
let sealed = Object.seal({})
Reflect.isExtensible(sealed)  // === false
// Frozen objects are also by definition non-extensible.
let frozen = Object.freeze({})
Reflect.isExtensible(frozen)  // === false
					

Difference to Object.isExtensible()

若 target argument to this method is not an object (a primitive), then it will cause a TypeError . With Object.isExtensible() , a non-object first argument will be coerced to an object at first.

Reflect.isExtensible(1)
// TypeError: 1 is not an object
Object.isExtensible(1)
// false
					

规范

规范
ECMAScript (ECMA-262) The definition of 'Reflect.isExtensible' 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
isExtensible	Chrome 49	Edge 12	Firefox 42	IE No	Opera 36	Safari 10	WebView Android 49	Chrome Android 49	Firefox Android 42	Opera Android 36	Safari iOS 10	Samsung Internet Android 5.0	nodejs 6.0.0

图例

完整支持

完整支持

不支持

不支持

另请参阅

• Reflect
• Object.isExtensible()

元数据

• 最后修改： Jan 30, 2020

相关话题

1. 标准内置对象
2. Reflect
3. 方法
   1. Reflect.apply()
   2. Reflect.construct()
   3. Reflect.defineProperty()
   4. Reflect.deleteProperty()
   5. Reflect.get()
   6. Reflect.getOwnPropertyDescriptor()
   7. Reflect.getPrototypeOf()
   8. Reflect.has()
   9. Reflect.isExtensible()
   10. Reflect.ownKeys()
   11. Reflect.preventExtensions()
   12. Reflect.set()
   13. Reflect.setPrototypeOf()
4. 继承：
5. Object
6. 特性
   1. Object.prototype.__proto__
   2. Object.prototype.constructor
7. 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()