javascript - 如何在原型(prototype)函数中访问javascript对象变量

Question

我有以下javascript

function person() {
  //private Variable
  var fName = null;
  var lName = null;

  // assign value to private variable
  fName = "Dave";
  lName = "Smith";
};

person.prototype.fullName = function () {
  return this.fName + " " + this.lName;
};

var myPerson = new person();
alert(myPerson.fullName());

我正在尝试了解 javascript 中面向对象的技术。我有一个简单的人对象，并在其原型(prototype)中添加了一个函数。

我原以为警报会显示“Dave Smith”，但我得到的是 “underfined underfined”。为什么会这样，我该如何解决？

Answer 1

很遗憾，您无法访问私有(private)变量。因此，要么将其更改为公共(public)属性，要么添加 getter/setter 方法。

function person() {

    //private Variable
    var fName = null;
    var lName = null;

    // assign value to private variable
    fName = "Dave";
    lName = "Smith";

    this.setFName = function(value){ fName = value; };
    this.getFName = function(){ return fName; }
};

参见 javascript - accessing private member variables from prototype-defined functions

---

但实际上这看起来像您要找的东西: Javascript private member on prototype

来自那个 SO 帖子:

As JavaScript is lexically scoped, you can simulate this on a per-object level by using the constructor function as a closure over your 'private members' and defining your methods in the constructor, but this won't work for methods defined in the constructor's prototype property.

在你的情况下:

var Person = (function() {
    var store = {}, guid = 0;

    function Person () {
        this.__guid = ++guid;
        store[guid] = { 
            fName: "Dave",
            lName: "Smith"
        };
    }

    Person.prototype.fullName = function() {
        var privates = store[this.__guid];
        return privates.fName + " " + privates.lName;
    };

    Person.prototype.destroy = function() {
        delete store[this.__guid];
    };

    return Person; 
})();


var myPerson = new Person();

alert(myPerson.fullName());

// in the end, destroy the instance to avoid a memory leak
myPerson.destroy();

查看现场演示 http://jsfiddle.net/roberkules/xurHU/