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

私有函数不能使用模块模式访问公共变量

其他回答

模块模式的典范:揭示模块模式

一个非常健壮的模式的简洁的小扩展。

就我个人而言,我更喜欢用JavaScript创建类的以下模式:

var myClass = (function() {
    // Private class properties go here

    var blueprint = function() {
        // Private instance properties go here
        ...
    };

    blueprint.prototype = { 
        // Public class properties go here
        ...
    };

    return  {
         // Public class properties go here
        create : function() { return new blueprint(); }
        ...
    };
})();

如您所见,它允许您定义类属性和实例属性,每个属性都可以是公共的和私有的。


Demo

var Restaurant = function() { var totalfoodcount = 0; // Private class property var totalrestroomcount = 0; // Private class property var Restaurant = function(name){ var foodcount = 0; // Private instance property var restroomcount = 0; // Private instance property this.name = name this.incrementFoodCount = function() { foodcount++; totalfoodcount++; this.printStatus(); }; this.incrementRestroomCount = function() { restroomcount++; totalrestroomcount++; this.printStatus(); }; this.getRestroomCount = function() { return restroomcount; }, this.getFoodCount = function() { return foodcount; } }; Restaurant.prototype = { name : '', buy_food : function(){ this.incrementFoodCount(); }, use_restroom : function(){ this.incrementRestroomCount(); }, getTotalRestroomCount : function() { return totalrestroomcount; }, getTotalFoodCount : function() { return totalfoodcount; }, printStatus : function() { document.body.innerHTML += '<h3>Buying food at '+this.name+'</h3>' + '<ul>' + '<li>Restroom count at ' + this.name + ' : '+ this.getRestroomCount() + '</li>' + '<li>Food count at ' + this.name + ' : ' + this.getFoodCount() + '</li>' + '<li>Total restroom count : '+ this.getTotalRestroomCount() + '</li>' + '<li>Total food count : '+ this.getTotalFoodCount() + '</li>' + '</ul>'; } }; return { // Singleton public properties create : function(name) { return new Restaurant(name); }, printStatus : function() { document.body.innerHTML += '<hr />' + '<h3>Overview</h3>' + '<ul>' + '<li>Total restroom count : '+ Restaurant.prototype.getTotalRestroomCount() + '</li>' + '<li>Total food count : '+ Restaurant.prototype.getTotalFoodCount() + '</li>' + '</ul>' + '<hr />'; } }; }(); var Wendys = Restaurant.create("Wendy's"); var McDonalds = Restaurant.create("McDonald's"); var KFC = Restaurant.create("KFC"); var BurgerKing = Restaurant.create("Burger King"); Restaurant.printStatus(); Wendys.buy_food(); Wendys.use_restroom(); KFC.use_restroom(); KFC.use_restroom(); Wendys.use_restroom(); McDonalds.buy_food(); BurgerKing.buy_food(); Restaurant.printStatus(); BurgerKing.buy_food(); Wendys.use_restroom(); McDonalds.buy_food(); KFC.buy_food(); Wendys.buy_food(); BurgerKing.buy_food(); McDonalds.buy_food(); Restaurant.printStatus();

看看这小提琴。

我更喜欢将私有数据存储在关联的WeakMap中。这允许你将你的公共方法保留在原型上。对于大量的对象,这似乎是处理这个问题的最有效的方法。

const data = new WeakMap();

function Foo(value) {
    data.set(this, {value});
}

// public method accessing private value
Foo.prototype.accessValue = function() {
    return data.get(this).value;
}

// private 'method' accessing private value
function accessValue(foo) {
    return data.get(foo).value;
}

export {Foo};

ES2021 / ES12 -私有方法

私有方法名以哈希前缀#开头,并且只能在定义它的类内部访问。

class Restaurant {

  // private method
  #private_stuff() {
    console.log("private stuff");
  }

  // public method
  buy_food() {
    this.#private_stuff();
  }

};

const restaurant = new Restaurant();
restaurant.buy_food(); // "private stuff";
restaurant.private_stuff(); // Uncaught TypeError: restaurant.private_stuff is not a function

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'