How can you get the file extension from a filename using JavaScript?

General Discussions
,
1

For example, given these filenames:

var file1 = "50.xsl";
var file2 = "30.doc";

How do you implement a function getFileExtension(filename) that returns xsl for file1 and doc for file2?

What’s the simplest way to achieve this using javascript get file extension techniques?

2

You can just split the filename by . and grab the last part like this:

function getFileExtension(filename) {
  return filename.split('.').pop();
}
So getFileExtension("50.xsl") returns "xsl".

It works well for simple filenames.

3

@mehta_tvara If you want to be safer and return an empty string when there’s no extension (like “file”), you can do:

function getFileExtension(filename) {
  const parts = filename.split('.');
  return parts.length > 1 ? parts.pop() : '';
}

That way, “filename” returns “” instead of the whole name.

4

If you want a quick, efficient way without splitting:

function getFileExtension(filename) {
  const dotIndex = filename.lastIndexOf('.');
  return dotIndex !== -1 ? filename.substring(dotIndex + 1) : '';
}

This finds the last dot and returns the substring after it.

It’s clean and fast.