handler.get()

The handler.get() method is a trap for the Get object internal method, which is used by operations such as property accessors.

Syntax

new Proxy(target, {
  get(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

Interceptions

This trap can intercept these operations:

Property access: proxy[foo] and proxy.bar
Reflect.get

Or any other operation that invokes the Get internal method.

Invariants

If the following invariants are violated, the trap throws a TypeError when invoked.

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(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(target, property) {
    return 20;
  },
});

p.a; // TypeError is thrown