Is it always safe to concatenate javascript files from different sources and load them as one ?

Question

I want to concatenate javascript files together and serve them as one from my site - so thats my code and jquery plugins or other 3rd party scripts. (I'm using google CDN for hosting of jQuery).

I was wondering i this is always guaranteed to be a safe thing to do. I'm not an expert in Javascript as far as things like namespacing goes and I was just a little worried that it might be possible to have something - like a namespace construct that could cause a conflict. I'm fine in assuming that the javascript is all well formed from each source.

As far as I know a <script> tag essentially just sticks the JS in place as if it was in the file, but I wondered if theres any boundary cases where this isn't true.

I'm aware that concatenation of files is something that is common and used by javascript frameworks such as Yahoo's YUI - but obviously they have full control of their files.

Answer 1

As long as you concatenate them in the correct order you should be safe. The correct order is the same order as you load them in today.

Answer 2

I'd have to agree with krosenvold no reason why it shouldn't work that I can think off. Just make sure you watch your global variables and function names, they could cause problems if you get the scripts from multiple non-collaborating sources.

Answer 3

You may run into syntax errors around semi-colons.

file A:

var foo = 3 // END OF FILE

file B:

var bar = 4 // BEGINNING OF FILE

file A+B:

var foo = 3var bar = 4

Easily solved by just jamming a semi-colon between each file you are concatenating.