javascript: 'this' 对象不可访问？

Question

我正在使用 here 中的示例。

    function Restaurant() {
        this.mongoose = 'beans';
        this.freedom = {bear: 'love', a: 12};
    
        var myPrivateVar;
    
        // Only visible inside Restaurant()
        var private_stuff = function() {
            myPrivateVar = "I can set this here!";
            this.mongoose = 12;
            this.freedom.a = 14; // <= 'a' undefined 2nd time
        }

        // use_restroom is visible to all    
        this.use_restroom = function() {
            private_stuff();
        }

        // buy_food is visible to all    
        this.buy_food = function() {
            private_stuff();
        }
    
        private_stuff.call(this);
    }
    
    var bobbys = new Restaurant();
    bobbys.buy_food() // <= fails

我在 private_stuff() 中将 this.freedom.a 设置为 14，然后调用 bobbys.buy_food()。当调用该函数时，this.freedom 显然是未定义的，所以我无法设置 a.

有人知道为什么它在 freedom 上失败而不在 mongoose 上失败吗？

感谢评论，但如果有人发帖 'Answer'，那么我可以将此作为已解决关闭，并感谢您。

Answer 1

    function Restaurant() {
        var ths = this;
        this.mongoose = 'beans';
        this.freedom = {bear: 'love', a: 12};
    
        var myPrivateVar;
    
        // Only visible inside Restaurant()
        var private_stuff = function() {
            myPrivateVar = "I can set this here!";
            this.mongoose = 12;
            ths.freedom.a = 14; // <= 'a' undefined 2nd time
        }

        // use_restroom is visible to all    
        this.use_restroom = function() {
            private_stuff();
        }

        // buy_food is visible to all    
        this.buy_food = function() {
            private_stuff();
        }
    
        private_stuff.call(this);
    }
    
    var bobbys = new Restaurant();
    bobbys.buy_food()

试试这个

Answer 2

现在应该可以了:)

只需在您的购买食物方法中使用调用即可。

function Restaurant() {
    this.mongoose = 'beans';
    this.freedom = {bear: 'love', a: 12};

    var myPrivateVar;

    // Only visible inside Restaurant()
    var private_stuff = function() {
        myPrivateVar = "I can set this here!";
        this.mongoose = 12;
        this.freedom.bear = 14; // <= 'a' undefined 2nd time
    }

    // use_restroom is visible to all    
    this.use_restroom = function() {
        private_stuff();
    }

    // buy_food is visible to all    
    this.buy_food = function(...args) {
        private_stuff.call(this, ...args);
    }

    private_stuff.call(this);
}

var bobbys = new Restaurant();
bobbys.buy_food()

Answer 3

如果您有兴趣正确使用此模式，其重点是完全避免 this（更不用说 .call(this)）。您的“私有”方法和属性只是闭包中的变量，并且 public methods/props 附加到本地对象，该对象可以是封闭的 this 也可以只是文字：

function Restaurant() {
    var self = this;  // or {}

    self.publicProp = '';

    var privateProp = '';

    var privateFunc = function() {
        privateProp = 'hello';
        self.publicProp = 'world';
    }

    self.publicFunc = function() {
        privateFunc();
        return privateProp;
    }
    
    // return self; // if used a literal above
}

var bobbys = new Restaurant();
console.log(bobbys.publicFunc())
console.log(bobbys.publicProp)

javascript: 'this' 对象不可访问？

javascript: 'this' object not accessible?

javascript

this