How to extract extension from filename string in Javascript?

Question

how would i get the File extension of the file in a variable? like if I have a file as 1.txt I need the txt part of it.

Answer 1

var x = "1.txt";
alert (x.substring(x.indexOf(".")+1));

note 1: this will not work if the filename is of the form file.example.txt
note 2: this will fail if the filename is of the form file

Answer 2

Use the lastIndexOf method to find the last period in the string, and get the part of the string after that:

var ext = fileName.substr(fileName.lastIndexOf('.') + 1);

Answer 3

I use code below:

var fileSplit = filename.split('.');
var fileExt = '';
if (fileSplit.length > 1) {
fileExt = fileSplit[fileSplit.length - 1];
} 
return fileExt;

Answer 4

This is the solution if your file has more . (dots) in the name.

<script type="text/javascript">var x = "file1.asdf.txt";
var y = x.split(".");
alert(y[(y.length)-1]);</script>

Answer 5

I would recommend using lastIndexOf() as opposed to indexOf()

var myString = "this.is.my.file.txt"
alert(x.substring(x.lastIndexOf(".")+1))

Answer 6

A variant that works with all of the following inputs:

• "file.name.with.dots.txt"
• "file.txt"
• "file"
• ""
• null

would be:

var re = /(?:\.([^.]+))?$/;

var ext = re.exec("file.name.with.dots.txt")[1];   // "txt"
var ext = re.exec("file.txt")[1];                  // "txt"
var ext = re.exec("file")[1];                      // undefined
var ext = re.exec("")[1];                          // undefined
var ext = re.exec(null)[1];                        // undefined