Javascript：IE event.preventDefault为null或不是对象 [英] Javascript: IE event.preventDefault is null or not an object

问题描述

我的代码在FF / Chrome / Everything中运行良好，除了IE（7/8都失败了，没有打算继续下去）。由于限制，我不能使用jQuery并且硬编码Javascript。问题出在IE上，我得到preventDefault为null或者不是对象。希望你们其中一个人有答案，这里是相关代码：

My code works fine in FF/Chrome/Everything except IE(failed in both 7/8, didn't bother going furthur down). Due to restrictions, I cannot use jQuery and am hard-coding the Javascript. The issue is with IE, I am getting "preventDefault is null or not an object". Hoping one of you has the answer, and here's relevant code:

AddEvent方法：

AddEvent Method:

function addEvent( obj, type, fn ) {  
  if ( obj.attachEvent ) {  
    obj['e'+type+fn] = fn;  
    obj[type+fn] = function(){obj['e'+type+fn]( window.event );}  
    obj.attachEvent( 'on'+type, obj[type+fn] );  
  } else  
    obj.addEventListener( type, fn, false );  
};

事件处理程序抛出错误：

Event handler throwing error:

function mousedown(e){  
  if(e.preventDefault){  
    e.preventDefault();  
  } else {  
    e.returnValue = false;  
    e.cancelBubble=true;  
  }
  //Processing   
};

此外，DOCTYPE和charset都在调用HTML页面上设置。任何想法，将不胜感激。错误在mousedown方法的if语句中抛出。

Also DOCTYPE and charset are both set on the calling HTML page. Any ideas would be appreciated. The error is thrown in the if statement for the mousedown method.

编辑：

由于这一事实抓住window.event确实修复了主要问题，我发现问题是代码的不同部分。基本上我在预先放置的元素的ontop上添加一个元素，然后将mousedown / mousemove事件注册到该div。在< div> 上触发事件时，就会发生错误。

Due to the fact that grabbing window.event did "fix" the main issue, I discovered the problem was a different section of code. Basically I am adding a element ontop of a pre-placed element, and then registering mousedown/mousemove events to that div. When firing the event on the <div>, THAT'S where the error is thrown.

这可能是什么由于我已将事件注册到2

Could this be something due to the fact that I have events registered to 2

rect = document.createElement('div');  
rect.className='square';  
rect.id='chooser_rectangle';  
rect.style.left=initx+'px';  
rect.style.top=inity+'px';  

addEvent(rect,"mousemove",mousemove);  
addEvent(rect,"mousedown",mousedown);  

推荐答案

在IE中，事件对象不作为第一个传递事件处理程序的参数。相反，它是一个全局变量：

In IE the event object is not passed as the first argument to an event handler. Instead it is a global variable:

function mousedown(e){
 var evt = e || window.event; // IE compatibility
 if(evt.preventDefault){  
  evt.preventDefault();  
 }else{  
  evt.returnValue = false;  
  evt.cancelBubble=true;  
 }
 //Processing   
};

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