handler.apply()

The handler.apply() method is a trap for a function call.

Syntax

const p = new Proxy(target, {
  apply: function(target, thisArg, argumentsList) {
  }
});

Parameters

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

target

The target 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

The handler.apply() method is a trap for a function call.

Interceptions

This trap can intercept these operations:

• proxy(...args)
• Function.prototype.apply() and Function.prototype.call()
• Reflect.apply()

Invariants

If the following invariants are violated, the proxy will throw a TypeError.

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.

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

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

Specifications

Browser compatibility

See also

• Proxy
• handler
• Function.prototype.apply()
• Function.prototype.call()
• Reflect.apply()