//判斷照片大小function getPhotoSize(obj){  photoExt=obj.value.substr(obj.value.lastIndexOf(".")).toLowerCase();//獲得文件后綴名  if(photoExt!='.jpg'){    alert("請上傳后綴名為jpg的照片!");    return false;  }  var fileSize = 0;  var isIE = /msie/i.test(navigator.userAgent) && !window.opera;        if (isIE && !obj.files) {          var filePath = obj.value;           var fileSystem = new ActiveXObject("Scripting.FileSystemObject");       var file = fileSystem.GetFile (filePath);             fileSize = file.Size;       }else {      fileSize = obj.files[0].size;     }   fileSize=Math.round(fileSize/1024*100)/100; //單位為KB  if(fileSize>=10){    alert("照片最大尺寸為10KB，請重新上傳!");    return false;  }}

<input type="file" id="imgFile" name="upload" style="width:150px;" onchange="getPhotoSize(this)"/>