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

handler.get() method is a trap for getting a property value.

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, {
  get: function(target, property, receiver) {
  }
});
					

参数

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

target

The target object.

property

The name or Symbol of the property to get.

receiver

Either the proxy or an object that inherits from the proxy.

返回值

get() method can return any value.

描述

handler.get() method is a trap for getting a property value.

Interceptions

This trap can intercept these operations:

• Property access: proxy [ foo ] and proxy . bar
• Inherited property access: Object.create( proxy )[ foo ]
• Reflect.get()

Invariants

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

• The value reported for a property must be the same as the value of the corresponding target object property if the target object property is a non-writable, non-configurable own data property.
• The value reported for a property must be undefined if the corresponding target object property is a non-configurable own accessor property that has undefined as its [[Get]] 属性。

范例

Trap for getting a property value

The following code traps getting a property value.

const p = new Proxy({}, {
  get: function(target, property, receiver) {
    console.log('called: ' + property);
    return 10;
  }
});
console.log(p.a); // "called: a"
                  // 10
					

The following code violates an invariant.

const obj = {};
Object.defineProperty(obj, 'a', {
  configurable: false,
  enumerable: false,
  value: 10,
  writable: false
});
const p = new Proxy(obj, {
  get: function(target, property) {
    return 20;
  }
});
p.a; // TypeError is thrown
					

规范

规范
ECMAScript (ECMA-262) The definition of '[[Get]]' 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
get	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
• Reflect.get()

元数据

• 最后修改： May 25, 2020

相关话题

1. 标准内置对象
2. Proxy/handler