handler.apply()

The handler.apply() method is a trap for the [[Call]] object internal method, which is used by operations such as function calls.

Try it

Syntax

js

new Proxy(target, {
  apply(target, thisArg, argumentsList) {
  }
});

Parameters

The following parameters are passed to the apply() method. this is bound to the handler.

target

The target callable object.

thisArg

The this argument for the call.

argumentsList

The list of arguments for the call.

Return value

The apply() method can return any value.

Description

Interceptions

This trap can intercept these operations:

Or any other operation that invokes the [[Call]] internal method.

Invariants

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

  • The target must be a callable itself. That is, it must be a function object.

Examples

Trapping a function call

The following code traps a function call.

js

const p = new Proxy(function () {}, {
  apply(target, thisArg, argumentsList) {
    console.log(`called: ${argumentsList}`);
    return argumentsList[0] + argumentsList[1] + argumentsList[2];
  },
});

console.log(p(1, 2, 3)); // "called: 1,2,3"
// 6

Specifications

Specification
ECMAScript Language Specification
# sec-proxy-object-internal-methods-and-internal-slots-call-thisargument-argumentslist

Browser compatibility

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See also