Js--call, arrow functions/anonymous functions

The this point in JS (a few simpler):

1. This point of the normal function points to the window;

The 2 object method points to the current object;

3. () = "Arrow function points to the object when defined;

Apply and call can change the current this point, but cannot change the direction of the arrow function

functionfoo () {return() = {    return() = {      return() ={Console.log (' ID: ', This. ID);    };  }; };}varF = Foo.call ({id:1});varT1 = F.call ({id:2}) () ();//id:1vart2 = f (). Call ({id:3}) ();//id:1varT3 = f () (). Call ({id:4});//id:1

The example above shows that the this of the arrow function cannot be changed, and conversely, if it is an ordinary anonymous function, it can be changed:

function foo () {  return () = {    function() {        Console.log (  this. id);   };};} var f1 = Foo.call ({id:1}) () ()//undefined; var f2 = foo (). Call ({id:1}) ()//undefined; var f3 = foo () (). Call ({id:1})//1

The first two this finally points to window, and the last point to {id:1}

Js--call, arrow functions/anonymous functions