this问题

Question

为什么打印 undefined？怎么才能让这段代码分别打印global，obj和inner

var scope = 'global';

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

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

obj.do();

Answer 1

最后对象志向window,window.scope,返回的才是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指向问题
JS函数不同执行环境下的this指向

Answer 4

首先，这段代码打印出来的应该是global不是undefined，然后你这种写法inner是不可能通过this.scope来调用的，剩下的就去看看this指向吧

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();