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Javascript bundling and module loading

I've recently been thrown in to clean up a project which has like 45-50 individual .js javascript files. I wonder what the best approach would be to decrease the loading size of them all. Just concatenate all files into one with npm or gulp? Install some module loader? webpack?

If you're already concatenating, minifying, and uglifying and you don't want all the files to be loaded on all the pages due to a monolithic bundle, you might be looking for something like Webpack's Commons Chunk Plugin.
This plugin walks down the tree of dependencies for each endpoint defined in your Webpack.config file and determines which modules are required across all pages. It then breaks the code into two bundles, a "common" bundle containing the modules that every page requires, which you must load with a script tag on each page:
<script src="commons.js" charset="utf-8"></script>
And an endpoint bundle for each individual page that you reference normally in a script tag placed after the commons script tag:
<script src="specificpage.bundle.js" charset="utf-8"></script>
The result is that an individual page will not have to load modules that will only ever be used on other pages.
Again, this is a Webpack plugin. I don't know if this functionality is available as a Gulp plugin, because it must have knowledge of all endpoints in order to determine which dependencies are common to them all.

I redirect you to the very good https://github.com/thedaviddias/Front-End-Checklist
In particular the following advises:
JavaScript Inline: High You don't have any JavaScript code inline
(mixed with your HTML code).
Concatenation: High JavaScript files
are concatenated.
Minification: High JavaScript files are minified (you can add the .min suffix).
You can accomplish this with a package manager such as gulp, grunt or webpack (for the most famous ones). You just need to choose what you prefer to use.
If you consider webpack, You can start with my very simple (but understanding) starter: https://github.com/dfa1234/snippets-starter

There's no much thing that you can do, basically is:
Concatenation - https://www.npmjs.com/package/gulp-concat
Minification - https://www.npmjs.com/package/gulp-minify
Instead of creating all those scripts, you can get something to re-use on yeoman, f.e. the Fountain, so it will reduce a lot of time just typing procedural code for doing the concatenation/minification.
Also if you can use some lazy load (like RequireJS or some frameworks have support to lazy load the module, like Angular) that will improve the performance of your aplication
EDIT:
If you want even more performance, you can install some compression tool in your server, for example this one for NodeJS https://www.npmjs.com/package/compression

I'm my personal opinion, if you have time, the best approach would be to read and understand the purpose of the project. Then plan a proper refactor. You are not fixing anything with concatenating, this is just a deployment step.
You should analyze which technologies are being used and if you want to maintain this code, in the long run, make a proper refactor into a much more modern stack, maybe you can take a seed project with ES6, webpack, Babel... and create a proper repository well maintained with proper modularity and dependencies resolution.
Once you have that, decreasing the load its just about adding proper tools in build time (babel, webpack, etc).
You would like to add some unit tests and continue working properly :)

How to automate javascript version increment if file changed?

I'm using grunt to build a javascript/angularjs project in the following order:
clean copy > uglify > cssmin.
Now if I change a js file I'd always have to manually add a version increment at the end of the script tag, so that the browser can detect the changes.
<script src="/js/myscript?v123"></script>
Question: how can I automate this process using grunt? If I run the "grunt" command, only files that changed compared to the last run should get a version increment. So that the browser can reuse the cached files as much as possible.

I know short answers are not OK (not enough rep to comment), but you might want to checkout grunt-asset-cachebuster. I haven't tried it myself but there are plenty of examples in their npm page.
Also checkout this answer about grunt-newer

javascript: Run / Execute from Atom in Browser

While trying to learn javascript, I stumbled upon Typescript and decided to rather learn that. I installed Atom and the atom-typescript module and coded a typescript class, which compiles to a .js file. I created an index.html page with the .js in a script tag.
As far as I understand, in order to test the js code, I have to start a webserver and load index.html.
What would be a convenient way to do that? At least, I would like to manually run the script from Atom with a keyboard shortcut. Ideally, I would like the browser to refresh every time the typescript file changes in Atom.
No google result I could find explains how to do that, is that a difficult thing to do?

What would be a convenient way to do that?
Use browserify to reload your webapp everytime the JS changes. Also use nodemon to restart your webserver each time the backend JS changes.
Example:
Checkout http://typescriptbuilder.com/
Nodemon config:
https://github.com/TypeScriptBuilder/tsb/blob/master/nodemon.json
Wepack config:
https://github.com/TypeScriptBuilder/tsb/blob/master/src/webpack.config.ts
Webpack config during devtime:
https://github.com/TypeScriptBuilder/tsb/blob/8a7d48d71a8327d48822fa15eb52b9adb1953223/src/server/devtime.ts#L15-L82

Using coffeescript with nodemon

Currently i discover that i can use nodemon with coffeescript, without needing to generate the .JS files, searching about i discovery that forever can do the same.
I wonder if use in production will lead to performace issues. I do not think so, since the Nodemon and Forever generate the javascript files in the dark just one time, when the server starts, then is not needed to generate these javascript files to each user request, correct?
Thank you.

That is correct, but in a production environment you would not use nodemon because your source code (for your currently deployed version) is not supposed to change. Forever would be more appropriate in this game.

xcode 4 + phonegap ... not update JS upon build?

I've run into a weird issue that has had me scratching my head for the past hour.
I'm working on an iPad app using Xcode 4 and PhoneGap. It's using jQuery. I've put all my JS into a scripts.js file.
Things are working well.
I spend about an hour doing a lot of CSS tweaking. I'd update the CSS file, stop the app, rebuild, and push to the iPad simulator or my iPad. That's been working fine. Every update to the CSS file is reflected on the new build.
I then needed to update the JS file. I couldn't get things to work and then I finally realized none of my JS changes were actually be put into the build. I finally blanked out my JS file completely, rebuilt, and it's still not updating.
The file I'm updated is being updated in the finder in the project folder (I can right-click 'view in finder' and that file is, indeed, updated).
So I'm stumped. Is the xcode compiler caching the JS file somehow instead of grabbing the updated file? Is there a way to force it to grab the updated JS?

I found it necessary to hold the Option button when clicking the menu command which turns the command from "Clean" to "Clean Build Folder..." and this caused my assets to be refreshed.

Well, after some more googling, this seems to be a common problem. Xcode seems to cache files even after you've edited them.
One option appears to be to run the 'clean' command before a new build. I tried that, no luck.
Other solutions appear to involve rebuilding the .plist file each time. I don't fully understand that (yet) in terms of how to do that automatically, but did find this workaround:
Open your .plist file
change something (in my case, I rename one of the app icon files each time)
save and build
Doing that magically forces xcode to FINALLY grab all the updated files and do a proper build.
I can't explain why Xcode seems perfectly happy grabbing my updated .css file each and every time but won't update the .html or or .js files without first doing this .plist file edit.
Seems as if Apple still has a few bugs to work out. I guess we'll have to wait patiently for the next 4gig .x relase of it. ;)

Just add a new "Run Script" build phase to your target in XCode and paste this :
touch -cm ${SRCROOT}/www

I do not have mac right now, but few things to try:
Try to look at Your project build (or prebuild or something) action where www folder is supposed to be copied.
Try to change index.html and see if it works.
Try to copy paste all Your javascript code to index.html script tag
Try to validate Your javascript (For example: Google Closure Compiler) and see if it has no problems

None of these worked for me :(
The only way I can get the thing to update its html and js is by running a "corodova run ios" at the command line.

Find the file called copy-www-build-step.sh.
Mine was in [project_folder]/platforms/ios/cordova/lib/copy-www-build-step.sh
In that file, find the lines beginning rsync -a "...
Add -c to the rsync lines, so they ready rsync -a -c "...
copy-www-build-step.sh is the script that copies the files over from www/ to where they go inside the app file. rsync is the unix file copying command they use. Without that -c, rsync just compares the file size on each file and folder and copies them over if the size has changed, and a couple of spaces or quotes don't count as enough of a change. With the -c, it checksums them and compares the checksums, which will catch even the smallest changes.
I think this will work best, because it's not a workaround, it actually fixes the cause of the problem.

I just had this issue, and the build phase command posted here (which is actually now used by the default Phonegap project) did not work for me, since I am editing my files on a Parallels Windows VM, in Visual Studio.
What I did, was use this instead, in the Build Phase of my project:
find "${PROJECT_DIR}/www/." -exec touch -cm {} \;
Thats basically a recursive touch. I then set up Visual Studio to always reload the file, if it has been saved. Hope this helps.

I'm not sure which did it, but I did the following:
Changed an icon value in my MyProject-Info.plist
Quit the simulator
Product -> (hold option) -> Clean Build Folder
Run

I had this same issue with the iOS Simulator, I tried most of the suggestions above with no success, it would not pick up my changes.
Later another possible solution occurred to me, which did work:
Delete the app from the simulator. (ie. Click and hold on the icon, then hit the X when it starts to shake, then Hardware Home)
Then re-run from xCode.
(NB: "cordova build ios" was also required)

Nothing solution of above work
finally i saw there are two index.html file and .js file in the project created using Command line tool of Cordova
So make changes as below shown under Staging folder