What's with the random Javascript errors?-Collection of common programming errors

OK. While it’s more or less impossible to give a reasonable solution to such a general question, I’ll just add my 2 cents’ worth:

One possible source of “undefined variable” errors comes from including several scripts, which may or may not always load and execute in the same order. If you define a variable in one script (let’s call that script declare.js) and use it in another (let’s say use.js), and use.js is executed before declare.js, then you will get such an error. If the scripts execute the other way around, everything will appear fine.

If you’re interested in this very topic, have a look at e.g. Steve Souders’ book Even faster web sites, published by O’Reilly. More specifically, look at the chapter about non-blocking script loading.

Originally posted 2013-11-09 23:11:58.