I have a website, which uses different javascript plugins, and a bunch of js files to run (~30). I wanted to try to group these js files into a single file, and tried to apply a basic minification to it(only removing whitespaces) using Google's Closure Compiler.
I've introduced all of the js files, in the same order as they are included in my page to the Closure Compilers online version, and run the compilation. The parameters for the compilation looked like this:
// ==ClosureCompiler==
// @output_file_name default.js
// @compilation_level WHITESPACE_ONLY
// .... bunch of javascript files here
// ==/ClosureCompiler==
The compilation ran with success, there were neither warnings nor errors. I then fetched the result file, copied it to my server, and tried to include it to my page.
The page runs, but a strange error appears, which stops my javascript in the middle of it's operation:
TypeError: event.feature.values_ is undefined
I've tried to fetch the space where this error is happening, the code there looks something like this:
this.vectorLayer.getSource().on("addfeature",function(event){if(typeof event.feature.values_.type=="undefined")return;
This is something which my own javascript code is doing, but this part of the code shouldn't even run when the page is loading. When I use the separate javascript files, the page loads just greatly, without any errors, but with the white-space removed, and the files combined, this error appears.
With basic logic, I tought that by adding together the .js files in the same order in which they are included on my page, and only removing the white-spaces to get a smaller file size shouldn't result in any errors, as the browser loads the js files in synchronously anyways. Am I mistaken in this regard? If not, what could the possible reason for this error be?
EDIT 1:
Okay, so I narrowed down the problem to a single .js file, the javascript file of OpenLayers. If I do not compile that file, and include it separatly, everything works fine. What could be causing this strange problem?
As it turns out, this was caused by a strange caching mechanism on Google's side. Restarting the Closure Compiler, and reintroducing all the js files once again, then recompiling it, solved my problem.
Thanks for the comments guys!