Pass an object's method to a function in Javascript. Is this the correct interpretation of the-CodePudding

I was in an interview, and there was this question:

When the method X of an object O is passed to a function Y as a parameter, what happens if X contains a reference to 'this' and gets executed inside Y? Please provide code examples.

Is this code a correct interpretation of the question?

let O = {
  name: 'John',
  age: 30,
  X() {
    console.log(this.name);
  },
};
let generic = O.X();

function Y(param) {
  return param;
}
console.log(Y(generic));

Could you please help me understand and reply to the question, even if just with an example?

CodePudding user response：

The question asks if the function is passed, not if the function is invoked immediately, then passed. They were probably thinking of something like this:

let O = {
  name: 'John',
  age: 30,
  X() {
    console.log(this.name);
  },
};
function callbackInvoker(fn) {
  fn();
}
callbackInvoker(O.X);

As you can see, unless the passed method is bound first, or is an arrow function, its this binding to the O object will have been lost, which is probably what the question was intending to test you about.

CodePudding user response：


let O = {
  name: 'John',
  age: 30,
  X() {
    console.log(this.name);
  },
};
let generic = O.X;

function Y(fn) {
  return fn(); // <-- execute here
}
console.log(Y(generic));