JavaScript Development Essay 1: The Necessity of PreventDefault

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JavaScript Development Essay 1: The Necessity of PreventDefault_javascript Skills

May 16, 2016 pm 05:58 PM

If you don't add it, it seems that the problem only occurs in ie6. It has happened: changing the image address, the image disappeared, loading the style, but the style file is gone. Just like interrupting the download of resources, the correct explanation is that when using the A element as a button under IE6, you must remember to call preventDefault() in the onclick event. IE6 will forcefully close the currently active HTTP connection, resulting in the request being Other resources or scripts are not loading properly. But if the resource has been cached, there will be no such problem

Copy code The code is as follows:

 
<!DOCTYPE HTML> 
<html> 
<head> 
</head> 
<body> 
<h2> will appear in ie6, click Changing the image src causes the image not to appear. You need to preventDefault or return false</h2> 
<a id="J_btn" href="javascript:void(0)">Click to change the image address</a> 
<img id="J_img" height="160" src='http://www.baidu.com/img/baidu_sylogo1.gif' /> 
<script type="text/javascript" > 
var $ =function(id){return typeof (id) ==="string"? document.getElementById(id) : null}; 
var logo_bd ='http://www.baidu.com /img/baidu_sylogo1.gif'; 
var logo_go ='http://www.google.com.hk/intl/zh-CN/images/logo_cn.png' 
$("J_btn").onclick =function(event){ 
event = event || window.event; 
//event.preventDefault ? event.preventDefault() : event.returnValue = false; 
$("J_img").src = $("J_img").src == logo_bd ? logo_go : logo_bd; 
} 
</script> 
</body> 
</html> 

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