File gif,png,jpg,pdf upload check

<br /><script language="JavaScript"> <br />function develop_validation() <br />{ <br /> <br /> var fileupload3=document.selectdate.fileupload1.value; <br /> if(fileupload3==""){ <br /> alert("Please Upload Video");document.selectdate.fileupload3.focus();return false; <br /> } <br /> <br /> if(fileupload3 != "" ) <br /> { <br /> if (valupfile(fileupload3,"Thumbnail Image should be in jbg or gif or png") == false) <br /> { <br /> document.selectdate.fileupload3.select(); <br /> return false; <br /> } <br /> } <br /> <br /> <br /> <br /> return true; <br /> <br />} <br /> <br /> <br />//function valupfile(field,alerttxt) <br />//{ <br />// with (field) <br />// { <br />// var dotjpg = field.lastIndexOf(".jpg") <br />// var dotgif = field.lastIndexOf(".gif") <br />// var dotpng = field.lastIndexOf(".png") <br />// <br />// if(dotjpg >= 0) <br />// return true; <br />// else if(dotgif >= 0) <br />// return true; <br />// else if(dotpng >= 0) <br />// return true; <br />// else <br />// { <br />// alert(alerttxt) <br />// return false; <br />// } <br />// } <br />//} <br /> <br /> <br /></script> <br /> <br /> <br />