如何在构造函数中设置javascript私有变量？

Question

假设我有一个调用的javascript函数/类Foo,它有一个名为的属性bar.我希望在bar实例化类时提供值,例如:

var myFoo = new Foo(5);

将设为myFoo.bar5.

如果我创建bar一个公共变量,那么这是有效的,例如:

function Foo(bar)
{
    this.bar = bar;
}

但是,如果我想将其设为私有,例如:

function Foo(bar)
{
   var bar;
}

那么我如何设置私有变量的值bar,使其可用于所有内部函数foo？

Answer 1

关于javascript中私有和受保护访问的最佳教程之一是:http://javascript.crockford.com/private.html.

function Foo(a) {
    var bar = a;                              // private instance data

    this.getBar = function() {return(bar);}   // methods with access to private variable
    this.setBar = function(a) {bar = a;}
}

var x = new Foo(3);
var y = x.getBar();   // 3
x.setBar(12);
var z = x.bar;        // not allowed (x has no public property named "bar")

Answer 2

您必须在构造函数中放置需要访问私有变量的所有函数:

function Foo(bar)
{
  //bar is inside a closure now, only these functions can access it
  this.setBar = function() {bar = 5;}
  this.getBar = function() {return bar;}
  //Other functions
}

var myFoo = new Foo(5);
myFoo.bar;      //Undefined, cannot access variable closure
myFoo.getBar(); //Works, returns 5