Why is function.apply.length 2 in JavaScript?

Question

When I run this code on console:

(function test(){
   console.log(function(){}.apply.length);
})();

The output is: 2

I read about Function length. I understand the function length section on MDN. But I don't understand this. There are no parameters in function. Why is the output 2?

Answer 1

It's because you're asking for the .length of Function.prototype.apply, which is 2 for its thisArg and its argArray.

19.2.3.1Function.prototype.apply ( thisArg, argArray ) <-- two parameters

Answer 2

Because of apply which accepts 2 parameters. Without apply it will show 0

(function test() {
  console.log(function() {}.length)
})();