Question

前一段时间我选择了this book来帮助理解如何将我在Java中的设计模式知识应用到Web开发中。但是，我在介绍中遇到了一个奇怪的差异。

作者声明以下代码定义了一个允许用户创建动画对象的类：

//Anim class

var Anim = function(){ /*code here*/ };
Anim.prototype.start = function(){ /*start code here*/ };
Anim.prototype.stop = function() { /*stop code here */};

//create a new Anim object and call the start method
var newAnim = new Anim();
newAnim.start();

我尝试了与我的应用程序类似的东西。

//Nucleus class and addLink function
var Nucleus = function(){
  this.location=null;
  this.links = [];
}

//revamp object and add to link array
Nucleus.prototype.addLink = function(marker){  }

上述类通过

实例化为全局变量

var curSpot = new Nucleus();

但是，Firebug在页面加载时抛出错误，指出Nucleus is not a constructor，并且禁用了Javascript按钮处理功能。通过将Nucleus定义更改为

来解决问题

function Nucleus(){ /*instance members here*/ }

现在OO功能正常运行。为什么后一个例子有用，但这本书的例子会引发错误？

应Ryan Lynch的要求，发布了更多代码。这是使用1curStop的唯一代码。作为一个全局变量，

//global variables
var curStop = new Nucleus();

function showMarkers(){
//unreleated code here

  var tourList = [];

  //handles a double click event, adds current marker to list and creates one
  //if not null.  Otherwise, create a new Nucleus object and add current location
  (function(marker){
    google.maps.event.addListener(marker, 'dblclick', function(){
      if (curStop != null){
        tourList.push(curStop);
        curStop = null;

      } else {
        curStop = new Nucleus();
        curStop.addLocation(marker);
      }
    }); //end listener
  })(marker);
}

function postTour(){

  //need CurStop to be a global variable, since only new double-click events add the
  //object to the tourList array.  This makes sure that all objects are saved on
  //button click
  tourList.push(curStop);
}

了解Javascript设计模式中的差异

0 个答案: