66 - this

The result is an error.

function createUser() {
  return {
    name: "John Doe",
    ref: this
  };
}

let user = createUser();

alert(user.ref.name); 
// Error: Cannot read property 'name' of undefined

This occurs because the rules governing this do not consider object definitions. Instead, they depend on the moment of function invocation.

Within the createUser() function, the value of this is undefined because it is invoked as a function, not as a method with dot syntax.

The value of this remains consistent throughout the entire function, unaffected by code blocks or object literals. Therefore, ref: this captures the current this of the function.

We can rewrite the function to explicitly return this:

function createUser(){
  return this; // In this version, there's no object literal

}

alert(createUser().name); 
// Error: Cannot read property 'name' of undefined

Notice that the result of alert(createUser().name) mirrors the outcome of alert(user.ref.name) from the previous example.

Alternatively, when ref is defined as a method, this is properly bound:

function createUser() {
  return {
    name: "John Doe",
    ref() {
      return this;
    }
  };
}

let user = createUser();

alert(user.ref().name); // John Doe

Here, user.ref() acts as a method, and this is correctly set to the object before the dot.