How can I get file extensions with JavaScript?

Question

See code:

var file1 = \"50.xsl\";
var file2 = \"30.doc\";
getFileExtension(file1); //returns xsl
getFileExtension(file2); //returns doc

function getFileExt         


        

Answer 1

Newer Edit: Lots of things have changed since this question was initially posted - there's a lot of really good information in wallacer's revised answer as well as VisioN's excellent breakdown

---

Edit: Just because this is the accepted answer; wallacer's answer is indeed much better:

return filename.split('.').pop();

---

My old answer:

return /[^.]+$/.exec(filename);

Should do it.

Edit: In response to PhiLho's comment, use something like:

return (/[.]/.exec(filename)) ? /[^.]+$/.exec(filename) : undefined;

Answer 2

Don't forget that some files can have no extension, so:

var parts = filename.split('.');
return (parts.length > 1) ? parts.pop() : '';

Answer 3

function getFileExtension(filename)
{
  var ext = /^.+\.([^.]+)$/.exec(filename);
  return ext == null ? "" : ext[1];
}

Tested with

"a.b"     (=> "b") 
"a"       (=> "") 
".hidden" (=> "") 
""        (=> "") 
null      (=> "")  

Also

"a.b.c.d" (=> "d")
".a.b"    (=> "b")
"a..b"    (=> "b")

Answer 4

return filename.replace(/\.([a-zA-Z0-9]+)$/, "$1");

edit: Strangely (or maybe it's not) the $1 in the second argument of the replace method doesn't seem to work... Sorry.

Answer 5

If you are dealing with web urls, you can use:

function getExt(filepath){
     return filepath.split("?")[0].split("#")[0].split('.').pop();
}

getExt("../js/logic.v2.min.js") // js
getExt("http://example.net/site/page.php?id=16548") // php
getExt("http://example.net/site/page.html#welcome.to.me") // html
getExt("c:\\logs\\yesterday.log"); // log

Demo: https://jsfiddle.net/squadjot/q5ard4fj/

Answer 6

function getExt(filename)
{
    var ext = filename.split('.').pop();
    if(ext == filename) return "";
    return ext;
}