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Proxy.handler.get

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

Syntax

var p = new Proxy(target, {
  get: function(target, property, receiver) {
  }
});

Parameters

The following parameters are passed to the get method. 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.

Return value

The get method can return any value.

Description

The 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 data property.
  • The value reported for a property must be undefined if the corresponding target object property is non-configurable accessor property that has undefined as its [[Get]] attribute.

Examples

The following code traps getting a property value.

var 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.

var obj = {};
Object.defineProperty(obj, 'a', { 
  configurable: false, 
  enumerable: false, 
  value: 10, 
  writable: false 
});

var p = new Proxy(obj, {
  get: function(target, property) {
    return 20;
  }
});

p.a; // TypeError is thrown

Specifications

Browser compatibilityUpdate compatibility data on GitHub

Desktop
Chrome Edge Firefox Internet Explorer Opera Safari
Basic support 49 12 18 No 36 10
Mobile
Android webview Chrome for Android Edge Mobile Firefox for Android Opera for Android iOS Safari Samsung Internet
Basic support 49 49 Yes 18 36 10 5.0
Server
Node.js
Basic support 6.0.0

See also

© 2005–2018 Mozilla Developer Network and individual contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/handler/get