Node.js get file extension

Question

Im creating a file upload function in node.js with express 3.

I would like to grab the file extension of the image. so i can rename the file and then append the file

Answer 1

path.extname will do the trick in most cases. However, it will include everything after the last ., including the query string and hash fragment of an http request:

var path = require('path')
var extname = path.extname('index.html?username=asdf')
// extname contains '.html?username=asdf'

In such instances, you'll want to try something like this:

var regex = /[#\\?]/g; // regex of illegal extension characters
var extname = path.extname('index.html?username=asdf');
var endOfExt = extname.search(regex);
if (endOfExt > -1) {
    extname = extname.substring(0, endOfExt);
}
// extname contains '.html'

Note that extensions with multiple periods (such as .tar.gz), will not work at all with path.extname.