下面的代码，需要保存到本地种执行，在线看不到实际效果。 <title>validate before upload by Lance Zhang</title> <form name="Myform"> <p> <font color="red" size="6">File type :gif,jpg,jpeg,png,bmp</font></p> <p> File Size limit: <input type="text" size="4" value="100" name="fileSizeLimit" id="fileSizeLimit"> K</p> <p> Image Height Limit: <input type="text" size="4" value="100" name="heightLimit" id="heightLimit"> </p> <p> Image Width Limit: <input type="text" size="4" value="100" name="widthLimit" id="widthLimit"> </p> <p> <input type="file" name="photo" onchange="changeSrc(this)"> Image Preview<img src="about:blank" id="fileChecker" name="fileChecker" alt="图片上传之前检查大小、尺寸、格式并预览的js代码_图象特效"> </p> <p> <input type="submit" value="submit"> </p> </form> [Ctrl A 全选 注:如需引入外部Js需刷新才能执行] function CheckFileSize() { var limit = document.getElementById("fileSizeLimit").value * 1024; var width = document.getElementById("widthLimit").value ; var height = document.getElementById("heightLimit").value; if (oFileChecker.fileSize > limit) { alert("FileSize :"+oFileChecker.fileSize+"byte--too large!"); } else { alert("FileSize :"+oFileChecker.fileSize+"byte--ok"); } if( oFileChecker.height> height) { alert("ImageHeight :"+oFileChecker.height+"--too height!"); } else { alert("ImageHeight :"+oFileChecker.height+"--ok"); } if(oFileChecker.width> width) { alert("ImageWidth :"+oFileChecker.width+"--too width!"); } else { alert("ImageWidth :"+oFileChecker.width+"--ok"); } return false; } var right_type=new Array(".gif",".jpg",".jpeg",".png",".bmp"); var oFileChecker = document.getElementById("fileChecker"); function changeSrc(filePicker) { if(!checkImgType(filePicker.value)) { alert("the file type is not correct"); return; } oFileChecker.src = filePicker.value; } oFileChecker.onreadystatechange = function () { if (oFileChecker.readyState == "complete") { CheckFileSize(); } } function checkImgType(fileURL) { var right_typeLen=right_type.length; var imgUrl=fileURL.toLowerCase(); var postfixLen=imgUrl.length; var len4=imgUrl.substring(postfixLen-4,postfixLen); var len5=imgUrl.substring(postfixLen-5,postfixLen); for (i=0;i<right_typeLen;i++) { if((len4==right_type[i])||(len5==right_type[i])) { return true; } } }
