Скачать или смотреть How to Get NULL, EMPTY, or UNDEFINED File Type Extensions in JavaScript

Learn how to effectively handle file URL extensions in JavaScript so that you get `NULL`, `EMPTY`, or `UNDEFINED` when the file has no extension.
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This video is based on the question https://stackoverflow.com/q/62282477/ asked by the user 'Owais' ( https://stackoverflow.com/u/6688223/ ) and on the answer https://stackoverflow.com/a/62282746/ provided by the user 'Ilijanovic' ( https://stackoverflow.com/u/10990737/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Get NULL, EMPTY, or UNDEFINED File Type Extensions in JavaScript

When dealing with file URLs in JavaScript, it's not uncommon to encounter files that do not have an extension. In such cases, you might be looking for a way to handle these scenarios gracefully by returning NULL, EMPTY, or UNDEFINED for URLs that lack a file extension. This guide will explore a simple solution for this problem and provide you with the necessary code to achieve the desired result.

The Problem

Many applications rely on file extensions to determine the type of a file. However, URLs like the following illustrate a common challenge:

URL without extension: http://www.example.com/uploads/abc

URL with extension: http://www.example.com/uploads/def.png, http://www.example.com/uploads/xyz.pdf

When you attempt to extract the file extension from URLs lacking them, using a method such as .split('.').pop(), you may encounter unintended results. For example, using this method on the first URL would yield com/uploads/abc, which is far from what you intend.

The Solution

Let's break down how to address this issue effectively with a JavaScript function. The goal of the function is to return the last part of the URL (the file name) and then check if it contains an extension. If it doesn't, the function should return UNDEFINED.

Step-by-Step Solution

Split the URL: Use the / character to break apart the URL into its segments.

Reverse the Array: This allows you to grab the last segment of the URL, which should be the file name.

Check for Extensions: Split the file name by . and check if there's any content after the last ..

Return Results: If there is an extension, return it; if not, return UNDEFINED.

Implementation

Here's the JavaScript code that implements the above logic:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Code

Input strings: The code initializes three URLs – one without an extension, one with a .pdf, and another with .pdf.dot.more.dots.

Function getExt:

It first splits the URL by /, reverses the array to access the last URL segment (the file name).

It then checks if the file name contains a period (.). If it does, it splits again by . and returns the last segment (the extension).

If there is no extension present, it returns undefined.

Conclusion

Handling file URLs can sometimes be tricky, especially when some files lack extensions. With the approach outlined in this guide, you can effortlessly extract file extensions or get UNDEFINED for URLs without them. This simple yet effective method can enhance your application's ability to process file types accurately, ensuring a seamless user experience.

Feel free to reach out with any questions, and happy coding!