从原型定义函数访问私有成员变量

Question

从原型定义函数访问私有成员变量

是否有任何方法使“私有”变量(那些在构造函数中定义的变量)可用于原型定义的方法？

TestClass = function(){
    var privateField = "hello";
    this.nonProtoHello = function(){alert(privateField)};};TestClass.prototype.prototypeHello = function(){alert(privateField)};

这样做是可行的：

t.nonProtoHello()

但这并不是：

t.prototypeHello()

我习惯于在构造函数中定义我的方法，但出于以下几个原因，我不这么做了。

Answer 1

当我读到这篇文章时，这听起来像是一个艰巨的挑战，所以我决定想出一个办法。我想出的是疯狂但它完全有效。首先，我尝试在直接函数中定义类，这样您就可以访问该函数的一些私有属性。这可以让您获得一些私有数据，但是，如果您试图设置私有数据，您很快就会发现所有对象都将共享相同的值。var SharedPrivateClass = (function() { // use immediate function    // our private data    var private = "Default";    // create the constructor    function SharedPrivateClass() {}    // add to the prototype    SharedPrivateClass.prototype.getPrivate = function() {        // It has access to private vars from the immediate function!        return private;    };    SharedPrivateClass.prototype.setPrivate = function(value) {        private = value;    };    return SharedPrivateClass;})();var a = new SharedPrivateClass();console.log("a:", a.getPrivate()); // "a: Default"var b = new SharedPrivateClass();console.log("b:", b.getPrivate()); // "b: Default"a.setPrivate("foo"); // a Sets private to "foo"console.log("a:", a.getPrivate()); // "a: foo"console.log("b:", b.getPrivate()); // oh no, b.getPrivate() is "foo"!console.log(a.hasOwnProperty("getPrivate")); // false. belongs to the prototypeconsole.log(a.private); // undefined// getPrivate() is only created once and instanceof still worksconsole.log(a.getPrivate === b.getPrivate);console.log(a instanceof SharedPrivateClass);console.log(b instanceof SharedPrivateClass);有很多情况下，这将是足够的，例如，如果您希望有常量的值，如事件名称，并在实例之间共享。但本质上，它们的作用就像私有的静态变量。如果您绝对需要从原型上定义的方法中访问私有命名空间中的变量，则可以尝试此模式。var PrivateNamespaceClass = (function() { // immediate function    var instance = 0, // counts the number of instances        defaultName = "Default Name",          p = []; // an array of private objects    // create the constructor    function PrivateNamespaceClass() {        // Increment the instance count and save it to the instance.         // This will become your key to your private space.        this.i = instance++;                 // Create a new object in the private space.        p[this.i] = {};        // Define properties or methods in the private space.        p[this.i].name = defaultName;                console.log("New instance " + this.i);            }    PrivateNamespaceClass.prototype.getPrivateName = function() {        // It has access to the private space and it's children!        return p[this.i].name;    };    PrivateNamespaceClass.prototype.setPrivateName = function(value) {        // Because you use the instance number assigned to the object (this.i)        // as a key, the values set will not change in other instances.        p[this.i].name = value;        return "Set " + p[this.i].name;    };    return PrivateNamespaceClass;})();var a = new PrivateNamespaceClass();console.log(a.getPrivateName()); // Default Namevar b = new PrivateNamespaceClass();console.log(b.getPrivateName()); // Default Nameconsole.log(a.setPrivateName("A"));console.log(b.setPrivateName("B"));console.log(a.getPrivateName()); // Aconsole.log(b.getPrivateName()); // B// private objects are not accessible outside the PrivateNamespaceClass functionconsole.log(a.p);// the prototype functions are not re-created for each instance// and instanceof still worksconsole.log(a.getPrivateName === b.getPrivateName);console.log(a instanceof PrivateNamespaceClass);console.log(b instanceof PrivateNamespaceClass);我希望任何看到错误的人都能给我一些反馈。