자바스크립트를 이용한 파일확장자 구하기

예1)

var fname="C:\\test\\text.txt";
var s=fname.lastIndexOf("\\");
var m=fname.lastIndexOf(".");
var e=fname.length;
var filename=fname.substring(s+1,m);
var extname=fname.substring(m+1,e);
alert(filename+"_"+extname);

예2)

var fname=document.all.myfile.value;
var arr=("file:///"+fname.replace(/ /gi,"%20").replace(/\\/gi,"/")).split("/");
alert(arr[arr.length-1]);

예3)

function getExtension() {
  var file = document.getElementsByName("upfile").item(0);
  var extension = file.value.replace( /%/,"%25").substr(file.value.replace( /%/,"%25").lastIndexOf(".")+1).toUpperCase();
  return extension;
}