How to Extract File Extensions with JavaScript?

How do I Get File Extensions with JavaScript?

Problem:

Consider the following code:

var file1 = "50.xsl";<br>var file2 = "30.doc";<br>getFileExtension(file1); //returns xsl<br>getFileExtension(file2); //returns doc</p>
<p>function getFileExtension(filename) {</p>
<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">/*TODO*/

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}

Question:

Complete the getFileExtension function to extract and return the file extension (e.g., xsl, doc).

Answer:

There are multiple ways to accomplish this:

1. Using .split and .pop:

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

   This splits the filename into an array using the . delimiter and returns the last element (the extension).

2. Using a Regular Expression:

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

   This regular expression starts by checking if the filename contains a period (.). If so, it then matches and returns the extension using a negative lookahead (prevents matching the period) and a $ (end of string) anchor.

   Note: If the filename does not contain a period (indicating no extension), it returns undefined to avoid returning an empty string.

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