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Proxy.proxy.get

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

Syntax

const 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 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]] attribute.

Examples

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

Specifications

Browser compatibilityUpdate compatibility data on GitHub

Desktop
Chrome Edge Firefox Internet Explorer Opera Safari
get 49 12 18 No 36 10
Mobile
Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet
get 49 49 18 36 10 5.0
Server
Node.js
get 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://wiki.developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/Proxy/get