Facebook编码技巧

Question

In an attempt to learn a little bit about Facebook and their coding techniques, I've viewed their source code. Here is one thing that I found:

<link rel="stylesheet" href="https://fbstatic-a.akamaihd.net/rsrc.php/v2/yN/r/JUrfX0ucXVq.css" />
<link rel="stylesheet" href="https://fbstatic-a.akamaihd.net/rsrc.php/v2/y2/r/gpxPzqCou0g.css" />
<link rel="stylesheet" href="https://fbstatic-a.akamaihd.net/rsrc.php/v2/yD/r/OWwnO_yMqhK.css" />

My question is about how Facebook composes their directory structure & filenames. Obviously the css files weren't named for readability. Is there a reason behind these random filenames? Could someone provide any information about this? Thanks in advance.

Answer 1

The CSS files are given random filenames to prevent browsers from caching them.

When a browser caches a resource, it will download the file and keep it on the user's computer to prevent the same file from being downloaded multiple times. The problem is that if you change your CSS file and keep the filename the same, a browser will keep using the cached version of the file and won't download the updated version. By giving the CSS files unique names, browsers are forced to download them.

It's similar to doing this with your CSS files:

<link rel="stylesheet" href="style-v1.css" />
<link rel="stylesheet" href="style-v2.css" />
<link rel="stylesheet" href="style-v3.css" />
...