After reading this article, I also understand this

// this Point to // 1. Point to Global variables window var a = 1;

function func() { var a = 2; console.log(this.a); } func(); //2 // 2. Point to the object that called it (funx() Medium this Only for immediate superiors （ Direct caller obj） be responsible for , No matter how many .) var b = 3;

function funx() { console.log(this.b); } var obj = { b: 4, funx } obj.funx(); //4

var aa = 15

function test() { console.log(this.aa) } var obj = { aa: 2, test } var obj0 = { aa: 3, obj } obj0.obj.test() // 3. You can pass it to a variable , And call it as well var d = 1

function test() { console.log(this.d) } var obj = { d: 2, test } var testCopy = obj.test testCopy(); // 4.call(), Who does the command point to var e = 7;

function test1() { console.log(this.e) } var obj = { e: 8, test1 } var testCopy = obj.test1 testCopy.call(obj); // 5. Point to the constructor instantiation object

More on ：https://blog.csdn.net/weixin_44519496/article/details/120126852