Question

我有以下对象。我试图从b的回调中到达变量setTimeout，但它不起作用。我知道setTimeout的回调只知道其周围函数的变量，那么我怎样才能到达this.b？谢谢！

function someFunc() {
    this.a = 10;
    this.b = 20;
    this.func = function() {
                this.c = 50;
        console.log("a = " + this.a);  //works
        var time = setTimeout(function() {
            console.log("b = " + someFunc.b);   //this.b doesn't work
            console.log("C = " + this.c);  //why this doesn't work also? says undefined
        },1000);
    }
}

var m = new someFunc();
m.func();

Answer 1

function someFunc() {
    this.a = 10;
    this.b = 20;
    var mySomeFunc = this;
    this.func = function() {
        console.log("a = " + this.a);  //works
        var time = setTimeout(function() {
            console.log("b = " + mySomeFunc.b);
        },1000);
    }
}

Answer 2

this不引用函数对象;它指的是调用它的上下文。（您的m变量）

someFunc.b是函数本身的属性（就像静态属性一样）您需要在变量中保存对外部this的引用。

Answer 3

此外，您可以使用类似的内容在对象范围内执行匿名函数：

function createDelegate(instance, callback) {
    return function () {
        callback.apply(instance, arguments);
    };
}

function someFunc() {
    this.a = 10;
    this.func = function() {
        this.c = 50;
        console.log("a = " + this.a);
        var time = setTimeout(createDelegate(this, function() {
            console.log("b = " + someFunc.b);
            console.log("C = " + this.c);
        }),1000);
    }
}

someFunc.b = 20;

var m = new someFunc();
m.func();

如何到达调用调用函数的函数的对象的变量

3 个答案: