JavaScript verification upload picture size [foreground processing]

Requirements Analysis:

When uploading pictures, if you do not limit the size of uploaded images, the consequences are very serious. So how can we solve a difficult problem? There are two ways of doing this:
1) Background processing: That is, Ajax Post submitted to the background, the picture uploaded to the server, and then get the image size to do processing.
2) Foreground processing: That is, using JavaScript to get the image size.
Obviously the first way, it's not good. Because the need to upload files to the server first, if the file is very large, in addition to the Internet is not very fast, need to wait for a long time, the symptoms do not cure.

Function Analysis:

Here I only introduce the different practices of IE and Firefox two browsers.
IE6:
Keyword: fileSize onreadystatechange complete
The file size can be obtained from the FileSize property of the IMG object in IE6, but the correct value of this FileSize property is set in the complete of the onReadyStateChange event, which is

 Function Sizecheck (img) {if (Img.readystate = = "complete") {alert (img.filesize); } }

FireFox3.0:
Keyword: getasdataurl () fileSize
In Firefox for security reasons, unable to get the full path of uploading pictures, only get the image name. However, the browser provides an interface such as nsidomfile, so you need to get the processed path through Getasdataurl (), but the path does not affect the image src display.
Nsidomfile Interface:

Domstring getasbinary (); Domstring Getasdataurl (); Domstring Getastext (in domstring encoding); <input type= "File" Name= "uploadimg" onchange= "Javascript:checkfilechange (this);"     Size= "/> function checkfilechange (obj) {var img = document.getElementById (" img ");     IMG.SRC = Obj.files[0].getasdataurl (); alert (obj.files[0].filesize); }

These are the two different browser processing methods, then how to bring them together? I'll post my little examples below, where I use jquery to facilitate and get objects

<! doctype html public  "-//w3c//dtd xhtml 1.0 transitional//en"   "HTTP// Www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd ">  

JavaScript verification upload picture size [foreground processing]