handler.get()

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

Try it

Syntax

js
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:

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.

js
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.

js
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

Specifications

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

Browser compatibility

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See also