handler.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

Specification
ECMAScript Language Specification (ECMAScript)
# sec-proxy-object-internal-methods-and-internal-slots-get-p-receiver

Browser compatibility

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See also