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 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, prop, receiver) {
    console.log('called: ' + prop);
    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, prop) {
    return 20;
  }
});

p.a; // TypeError is thrown

Specifications

Specification	Status	Comment
ECMAScript 2015 (6th Edition, ECMA-262) The definition of '[[Get]]' in that specification.	Standard	Initial definition.
ECMAScript 2017 Draft (ECMA-262) The definition of '[[Get]]' in that specification.	Draft

Browser compatibility

See also

• Proxy
• handler
• Reflect.get()