要创建一个带有公共方法的JavaScript类,我可以这样做:

function Restaurant() {}

Restaurant.prototype.buy_food = function(){
   // something here
}

Restaurant.prototype.use_restroom = function(){
   // something here
}

这样,我类的用户就可以:

var restaurant = new Restaurant();
restaurant.buy_food();
restaurant.use_restroom();

如何创建一个私有方法,可以由buy_food和use_restroom方法调用,但不能由类的用户外部调用?

换句话说,我希望我的方法实现能够做到:

Restaurant.prototype.use_restroom = function() {
   this.private_stuff();
}

但这是行不通的:

var r = new Restaurant();
r.private_stuff();

如何将private_stuff定义为私有方法,使两者都成立?

我读过Doug Crockford的文章几次,但它似乎不像“私有”方法可以被公共方法调用,而“特权”方法可以被外部调用。


当前回答

我知道有点晚了,但是这样怎么样?

var obj = function(){
    var pr = "private";
    var prt = Object.getPrototypeOf(this);
    if(!prt.hasOwnProperty("showPrivate")){
        prt.showPrivate = function(){
            console.log(pr);
        }
    }    
}

var i = new obj();
i.showPrivate();
console.log(i.hasOwnProperty("pr"));

其他回答

你必须在你实际的构造函数周围放一个闭包,在那里你可以定义你的私有方法。 要通过这些私有方法改变实例的数据,你必须给它们一个"this",要么作为函数参数,要么用.apply(this)调用这个函数:

var Restaurant = (function(){
    var private_buy_food = function(that){
        that.data.soldFood = true;
    }
    var private_take_a_shit = function(){
        this.data.isdirty = true;   
    }
    // New Closure
    function restaurant()
    {
        this.data = {
            isdirty : false,
            soldFood: false,
        };
    }

    restaurant.prototype.buy_food = function()
    {
       private_buy_food(this);
    }
    restaurant.prototype.use_restroom = function()
    {
       private_take_a_shit.call(this);
    }
    return restaurant;
})()

// TEST:

var McDonalds = new Restaurant();
McDonalds.buy_food();
McDonalds.use_restroom();
console.log(McDonalds);
console.log(McDonalds.__proto__);

这是我得出的结论:

需要一类糖代码,你可以在这里找到。还支持保护,继承,虚拟,静态的东西…

;( function class_Restaurant( namespace )
{
    'use strict';

    if( namespace[ "Restaurant" ] ) return    // protect against double inclusions

        namespace.Restaurant = Restaurant
    var Static               = TidBits.OoJs.setupClass( namespace, "Restaurant" )


    // constructor
    //
    function Restaurant()
    {
        this.toilets = 3

        this.Private( private_stuff )

        return this.Public( buy_food, use_restroom )
    }

    function private_stuff(){ console.log( "There are", this.toilets, "toilets available") }

    function buy_food     (){ return "food"        }
    function use_restroom (){ this.private_stuff() }

})( window )


var chinese = new Restaurant

console.log( chinese.buy_food()      );  // output: food
console.log( chinese.use_restroom()  );  // output: There are 3 toilets available
console.log( chinese.toilets         );  // output: undefined
console.log( chinese.private_stuff() );  // output: undefined

// and throws: TypeError: Object #<Restaurant> has no method 'private_stuff'

一个丑陋但有效的解决方案:

function Class(cb) { const self = {}; const constructor = (fn) => { func = fn; }; const addPrivate = (fnName, obj) => { self[fnName] = obj; } const addPublic = (fnName, obj) => { this[fnName] = obj; self[fnName] = obj; func.prototype[fnName] = obj; } cb(constructor, addPrivate, addPublic, self); return func; } const test = new Class((constructor, private, public, self) => { constructor(function (test) { console.log(test) }); public('test', 'yay'); private('qwe', 'nay'); private('no', () => { return 'hello' }) public('asd', () => { return 'this is public' }) public('hello', () => { return self.qwe + self.no() + self.asd() }) }) const asd = new test('qweqwe'); console.log(asd.hello());

这样的结局会让你付出代价。确保你在IE中测试了速度的影响。您会发现使用命名约定会更好。仍然有很多企业网络用户被迫使用IE6……

别啰嗦了。这是Javascript。使用命名约定。

在es6类工作了多年之后,我最近开始了一个es5项目(使用requireJS,它看起来已经非常冗长了)。我已经反复研究了这里提到的所有策略,基本上都可以归结为使用命名约定:

Javascript doesn't have scope keywords like private. Other developers entering Javascript will know this upfront. Therefore, a simple naming convention is more than sufficient. A simple naming convention of prefixing with an underscore solves the problem of both private properties and private methods. Let's take advantage of the Prototype for speed reasons, but lets not get anymore verbose than that. Let's try to keep the es5 "class" looking as closely to what we might expect in other backend languages (and treat every file as a class, even if we don't need to return an instance). Let's demonstrate with a more realistic module situation (we'll use old es5 and old requireJs).

my-tooltip.js

    define([
        'tooltip'
    ],
    function(
        tooltip
    ){

        function MyTooltip() {
            // Later, if needed, we can remove the underscore on some
            // of these (make public) and allow clients of our class
            // to set them.
            this._selector = "#my-tooltip"
            this._template = 'Hello from inside my tooltip!';
            this._initTooltip();
        }

        MyTooltip.prototype = {
            constructor: MyTooltip,

            _initTooltip: function () {
                new tooltip.tooltip(this._selector, {
                    content: this._template,
                    closeOnClick: true,
                    closeButton: true
                });
            }
        }

        return {
            init: function init() {
               new MyTooltip();  // <-- Our constructor adds our tooltip to the DOM so not much we need to do after instantiation.
            }

            // You could instead return a new instantiation, 
            // if later you do more with this class.
            /* 
            create: function create() {
               return new MyTooltip();
            }
            */
        }
    });