javascript - this question

Question

Why is undefined printed? How can I make this code print global, obj and inner respectively

var scope = 'global';

function log() {
    console.log(this.scope)
}

var obj = {
    scope: 'obj',
    do: function () {
        var scope = 'inner';
        log()
    }
};

obj.do();

Answer 1

The final object ambition is window, window.scope, and what is returned is undefined

Answer 2

var scope = 'global';

function log() {
    console.log(this.scope)
}

var obj = {
    scope: 'obj',
    do: function () {
        var scope = 'inner';
        log();
        console.log(scope);
    }
};
obj.do();
console.log(obj.scope);

Answer 3

this pointing problem
this pointing in different execution environments of JS functions

Answer 4

First of all, what this code prints should be global, not undefined. Then, it is impossible to call inner through this.scope the way you write it. For the rest, just look at the this pointer

Answer 5

var scope = 'global';

function log() {

console.log(this.scope)

}

var obj = {

scope: 'obj',
do: function () {
    var scope = 'inner';
    log();   //gobal
    console.log(this.scope);  //this指向obj,obj作用域中找到scope:obj
    console.log(scope);    //局部的inner
}

};

obj.do();