javascript - How to understand this code?

Question

var name = "123";

    var object = {
        name: "My Object",
        getNameFunc: function() {
            return this.name;
        }
    }
    console.log(object.getNameFunc());                            //My Object
    console.log((object.getNameFunc)());                        //My Object
    console.log((object.getNameFunc = object.getNameFunc)());    //123

Why is the final output 123? What does object.getNameFunc = object.getNameFunc mean?

Answer 1

I read the question wrong, let me explain it again.

First look at object.getNameFunc, its definition is

function () {
  return this.name
}

When you write like this object.getNameFunc = object.getNameFunc, it can actually be seen as like this.

object.getNameFunc = function () {
  return this.name
}

In fact, when doing such a thing, this is no longer an object. But window (in the browser). So the output is the external name.

Probably like this = =

Answer 2

The result of the assignment operation is an lvalue.

Therefore
(object.getNameFunc = object.getNameFunc)()
can be thought of as:

var f = (object.getNameFunc = object.getNameFunc); 
f(); 

So this points to the global, so we get 123

Answer 3

var name = "123";

var obj = {
    name: "My Object",
    getNameFunc: function() {
        return this.name;
    }
}
console.log(obj.getNameFunc());                            //My Object
console.log((obj.getNameFunc)());                        //My Object
console.log((obj.getNameFunc = obj.getNameFunc)());    //123
console.log((obj.getNameFunc = obj.getNameFunc));      

Judging from the citation results of this, this must be pointing to the overall situation. Maybe there are some links in the middle that are not understood.
If we add a piece of code at the end, we can know what the content of (obj.getNameFunc = obj.getNameFunc) is. Yes, there is a function in the console, so the statement (obj.getNameFunc = obj.getNameFunc) is executed The result is a function. Inertial thinking leads us to take it for granted that this is just a reassignment operation, and that it is still obj that calls the function.
In fact, after the statement is executed, this function is actually called by the global object.