之前有个工作需要用到js检查文件大小和文件格式，网上查了下有个兄弟写的不错，拿过来就能直接用，感谢他顺便记录下。原始文章地址http://www.jb51.net/article/43498.htm
<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <script type="text/javascript"> var isIE = /msie/i.test(navigator.userAgent) && !window.opera; function fileChange(target,id) { var fileSize = 0; var filetypes =[".jpg",".png",".rar",".txt",".zip",".doc",".ppt",".xls",".pdf",".docx",".xlsx"]; var filepath = target.value; var filemaxsize = 1024*2;//2M if(filepath){ var isnext = false; var fileend = filepath.substring(filepath.indexOf(".")); if(filetypes && filetypes.length>0){ for(var i =0; i<filetypes.length;i++){ if(filetypes[i]==fileend){ isnext = true; break; } } } if(!isnext){ alert("不接受此文件类型！"); target.value =""; return false; } }else{ return false; } if (isIE && !target.files) { var filePath = target.value; var fileSystem = new ActiveXObject("Scripting.FileSystemObject"); if(!fileSystem.FileExists(filePath)){ alert("附件不存在，请重新输入！"); return false; } var file = fileSystem.GetFile (filePath); fileSize = file.Size; } else { fileSize = target.files[0].size; } var size = fileSize / 1024; if(size>filemaxsize){ alert("附件大小不能大于"+filemaxsize/1024+"M！"); target.value =""; return false; } if(size<=0){ alert("附件大小不能为0M！"); target.value =""; return false; } } </script> </head> <body> <input type="file" name="contractFileName" style=" 500px;" onchange="fileChange(this);"/> </body> </html>