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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

handler.getOwnPropertyDescriptor() method is a trap for Object.getOwnPropertyDescriptor() .

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

const p = new Proxy(target, {
  getOwnPropertyDescriptor: function(target, prop) {
  }
});
					

参数

The following parameters are passed to the getOwnPropertyDescriptor() 方法。 this is bound to the handler.

target

The target object.

prop

The name of the property whose description should be retrieved.

返回值

getOwnPropertyDescriptor() method must return an object or undefined .

描述

handler.getOwnPropertyDescriptor() method is a trap for Object.getOwnPropertyDescriptor() .

Interceptions

This trap can intercept these operations:

• Object.getOwnPropertyDescriptor()
• Reflect.getOwnPropertyDescriptor()

Invariants

If the following invariants are violated, the proxy will throw a TypeError :

• getOwnPropertyDescriptor() must return an object or undefined .
• A property cannot be reported as non-existent, if it exists as a non-configurable own property of the target object.
• A property cannot be reported as non-existent, if it exists as an own property of the target object and the target object is not extensible.
• A property cannot be reported as existent, if it does not exists as an own property of the target object and the target object is not extensible.
• A property cannot be reported as non-configurable, if it does not exists as an own property of the target object or if it exists as a configurable own property of the target object.
• The result of Object.getOwnPropertyDescriptor( target ) can be applied to the target object using Object.defineProperty() and will not throw an exception.

范例

Trapping of getOwnPropertyDescriptor

The following code traps Object.getOwnPropertyDescriptor() .

const p = new Proxy({ a: 20}, {
  getOwnPropertyDescriptor: function(target, prop) {
    console.log('called: ' + prop);
    return { configurable: true, enumerable: true, value: 10 };
  }
});
console.log(Object.getOwnPropertyDescriptor(p, 'a').value); // "called: a"
                                                            // 10
					

The following code violates an invariant.

const obj = { a: 10 };
Object.preventExtensions(obj);
const p = new Proxy(obj, {
  getOwnPropertyDescriptor: function(target, prop) {
    return undefined;
  }
});
Object.getOwnPropertyDescriptor(p, 'a'); // TypeError is thrown
					

规范

规范
ECMAScript (ECMA-262) The definition of '[[GetOwnProperty]]' 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
getOwnPropertyDescriptor	Chrome 49	Edge 12	Firefox 18	IE No	Opera 36	Safari 10	WebView Android 49	Chrome Android 49	Firefox Android 18	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

• Proxy
• handler
• Object.getOwnPropertyDescriptor()
• Reflect.getOwnPropertyDescriptor()

元数据

• 最后修改： May 25, 2020

相关话题

1. 标准内置对象
2. Proxy/handler