Question: I wrote a PHP shell script which include queuing jobs in centOS with 'at' command.
The queue jobs may vary in time and contents which means the system need to keep quite a large number of jobs.
The application logic will also be a bit difficult to setup with cronjob.
Is there a limit in number of queue jobs in centOS or is there any alternative way of queuing jobs?

Answer: 
<http://eloquentjavascript.net/>

It may be a little wordy, but it gives you some excellent examples that will stick with ya.
The more you work with JavaScript/jQuery - especially working with other people's code - the more of the style you will pick up. I recommend reading though the documentation on the jQuery website and maybe picking up a book on Javascript. Then just keep working with it. Also, make sure you keep looking at other people's code - read through the source code of some of the jQuery plugins you are using, and seek out examples online for 'best practices'.