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。
var TestClass = function( ) {
var privateProperty = 42;
function privateMethod( ) {
alert( "privateMethod, " + privateProperty );
}
this.public = {
constructor: TestClass,
publicProperty: 88,
publicMethod: function( ) {
alert( "publicMethod" );
privateMethod( );
}
};
};
TestClass.prototype = new TestClass( ).public;
var myTestClass = new TestClass( );
alert( myTestClass.publicProperty );
myTestClass.publicMethod( );
alert( myTestClass.privateMethod || "no privateMethod" );
类似于georgebrock,但不太啰嗦(恕我直言)
这样做有什么问题吗?(我哪儿都没见过)
编辑:我意识到这有点没用,因为每个独立的实例化都有自己的公共方法副本,从而破坏了原型的使用。
以下是迄今为止我最喜欢的关于javascript中的私有/公共方法/成员和实例化:
这是文章:http://www.sefol.com/?p=1090
下面是一个例子:
var Person = (function () {
//Immediately returns an anonymous function which builds our modules
return function (name, location) {
alert("createPerson called with " + name);
var localPrivateVar = name;
var localPublicVar = "A public variable";
var localPublicFunction = function () {
alert("PUBLIC Func called, private var is :" + localPrivateVar)
};
var localPrivateFunction = function () {
alert("PRIVATE Func called ")
};
var setName = function (name) {
localPrivateVar = name;
}
return {
publicVar: localPublicVar,
location: location,
publicFunction: localPublicFunction,
setName: setName
}
}
})();
//Request a Person instance - should print "createPerson called with ben"
var x = Person("ben", "germany");
//Request a Person instance - should print "createPerson called with candide"
var y = Person("candide", "belgium");
//Prints "ben"
x.publicFunction();
//Prints "candide"
y.publicFunction();
//Now call a public function which sets the value of a private variable in the x instance
x.setName("Ben 2");
//Shouldn't have changed this : prints "candide"
y.publicFunction();
//Should have changed this : prints "Ben 2"
x.publicFunction();
JSFiddle: http://jsfiddle.net/northkildonan/kopj3dt3/1/
2021年这里!
这个polyfill有效地隐藏了你的私有属性和方法,当你试图读取你的私有属性时返回undefined,当你试图执行你的私有方法时返回TypeError,从而有效地使它们对外部都是private,但让你通过使用你的公共方法访问它们。
如果你检查它,你会发现它很容易实现。在大多数情况下,你不需要做任何奇怪的事情,如使用代理对象,下划线函数(_myprivate), getter或setter。都不是。唯一需要做的事情是在构造函数中放置一段类似的代码片段,目的是让您向外界公开您的公共接口。
((self) => ({
pubProp: self.pubProp,
// More public properties to export HERE
// ...
pubMethod: self.pubMethod.bind(self)
// More public mehods to export HERE
// Be sure bind each of them to self!!!
// ...
}))(self);
上面的代码就是魔术发生的地方。它是一个IIFE,返回一个对象,其中只包含您想要公开并绑定到第一次实例化的对象的上下文的属性和方法。
你仍然可以访问你的隐藏属性和方法,但只能通过你的公共方法,就像OOP应该做的那样。
将这部分代码视为module.exports
顺便说一句,这是没有使用最新的ECMAScript 2022 #添加到语言中。
'use strict';
class MyClass {
constructor(pubProp) {
let self = this;
self.pubProp = pubProp;
self.privProp = "I'm a private property!";
return ((self) => ({
pubProp: self.pubProp,
// More public properties to export HERE
// ...
pubMethod: self.pubMethod.bind(self)
// More public mehods to export HERE
// Be sure to bind each of them to self!!!
// ...
}))(self);
}
pubMethod() {
console.log("I'm a public method!");
console.log(this.pubProp);
return this.privMethod();
}
privMethod() {
console.log("I'm a private method!");
return this.privProp
}
}
const myObj = new MyClass("I'm a public property!");
console.log("***DUMPING MY NEW INSTANCE***");
console.dir(myObj);
console.log("");
console.log("***TESTING ACCESS TO PUBLIC PROPERTIES***");
console.log(myObj.pubProp);
console.log("");
console.log("***TESTING ACCESS TO PRIVATE PROPERTIES***");
console.log(myObj.privProp);
console.log("");
console.log("***TESTING ACCESS TO PUBLIC METHODS***");
console.log("1. pubMethod access pubProp ");
console.log("2. pubMethod calls privMethod");
console.log("3. privMethod access privProp");
console.log("")
console.log(myObj.pubMethod());
console.log("");
console.log("***TESTING ACCESS TO PRIVATE METHODS***");
console.log(myObj.privMethod());
看看我的主旨
模块模式在大多数情况下是正确的。但是如果您有数千个实例,类可以节省内存。如果需要考虑节省内存,并且您的对象包含少量私有数据,但有大量公共函数,那么您将希望所有公共函数都驻留在.prototype中以节省内存。
这是我想到的:
var MyClass = (function () {
var secret = {}; // You can only getPriv() if you know this
function MyClass() {
var that = this, priv = {
foo: 0 // ... and other private values
};
that.getPriv = function (proof) {
return (proof === secret) && priv;
};
}
MyClass.prototype.inc = function () {
var priv = this.getPriv(secret);
priv.foo += 1;
return priv.foo;
};
return MyClass;
}());
var x = new MyClass();
x.inc(); // 1
x.inc(); // 2
对象priv包含私有属性。它可以通过公共函数getPriv()访问,但该函数返回false,除非您将secret传递给它,并且只有在主闭包中才知道。
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());