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Traverse directory structure in Javascript with callback for each hit

There are a number of options for traversing a directory tree in Javascript (node-dir, fs.readdir, ...) and most supports asynchronous execution with a callback when finished.
But is there a framework that supports callbacks on each found file? I want to build a loader for audio files that incrementally adds the files as they are found.
Plain Javascript (or Typescript) solutions are also accepted.

I was thinking that traversing the structure was costly, and wanted to do the work for each file as it was found by the traversal, instead of collecting a list first. But experiments show that this is not the case, traversal is in fact very cheap compared to just opening a file, let alone parsing content. So I'll go with the suggestion from #Joseph and just use one of the options listed and call the function for each file.
I'll make this incremental by doing this asynchronously and update the UI reactively.
Thanks, for straightening out my thinking.

ES6 exports/imports use-case, compared to traditional namespacing

I don't understand WHY and in what scenario this would be used..
My current web setup consists of lots of components, which are just functions or factory functions, each in their own file, and each function "rides" the app namespace, like : app.component.breadcrumbs = function(){... and so on.
Then GULP just combines all the files, and I end up with a single file, so a page controller (each "page" has a controller which loads the components the page needs) can just load it's components, like: app.component.breadcrumbs(data).
All the components can be easily accessed on demand, and the single javascript file is well cached and everything. This way of work seems extremely good, never saw any problem with this way of work. of course, this can (and is) be scaled nicely.
So how are ES6 imports for functions any better than what I described?
what's the deal with importing functions instead of just attaching them to the App's namespace? it makes much more sense for them to be "attached".
Files structure
/dist/app.js // web app namespace and so on
/dist/components/breadcrumbs.js // some component
/dist/components/header.js // some component
/dist/components/sidemenu.js // some component
/dist/pages/homepage.js // home page controller
// GULP concat all above to
/js/app.js // this file is what is downloaded
Then inside homepage.js it can look like this:
app.routes.homepage = function(){
"use strict";
var DOM = { page : $('#page') };
// append whatever components I want to this page
DOM.page.append(
app.component.header(),
app.component.sidemenu(),
app.component.breadcrumbs({a:1, b:2, c:3})
)
};
This is an extremely simplified code example but you get the point

Answers to this are probably a little subjective, but I'm going to do my best.
At the end of the day, both methods allow support creating a namespace for a piece of functionality so that it does not conflict with other things. Both work, but in my view, modules, ES6 or any other, provide a few extra benefits.
Explicit dependencies
Your example seems very bias toward a "load everything" approach, but you'll generally find that to be uncommon. If your components/header.js needs to use components/breadcrumbs.js, assumptions must be made. Has that file been bundled into the overall JS file? You have no way of knowing. You're two options are
Load everything
Maintain a file somewhere that explicitly lists what needs to be loaded.
The first option is easy and in the short term is probably fine. The second is complicated for maintainability because it would be maintained as an external list, it would be very easy to stop needing one of your component file but forget to remove it.
It also means that you are essentially defining your own syntax for dependencies when again, one has now been defined in the language/community.
What happens when you want to start splitting your application into pieces? Say you have an application that is a single large file that drives 5 pages on your site, because they started out simple and it wasn't big enough to matter. Now the application has grown and should be served with a separate JS file per-page. You have now lost the ability to use option #1, and some poor soul would need to build this new list of dependencies for each end file.
What if you start using a file in a new places? How do you know which JS target files actually need it? What if you have twenty target files?
What if you have a library of components that are used across your whole company, and one of they starts relying on something new? How would that information be propagated to any number of the developers using these?
Modules allow you to know with 100% certainty what is used where, with automated tooling. You only need to package the files you actually use.
Ordering
Related to dependency listing is dependency ordering. If your library needs to create a special subclass of your header.js component, you are no longer only accessing app.component.header() from app.routes.homepage(), which would presumable be running at DOMContentLoaded. Instead you need to access it during the initial application execution. Simple concatenation offers no guarantees that it will have run yet. If you are concatenating alphabetically and your new things is app.component.blueHeader() then it would fail.
This applies to anything that you might want to do immediately at execution time. If you have a module that immediately looks at the page when it runs, or sends an AJAX request or anything, what if it depends on some library to do that?
This is another argument agains #1 (Load everything) so you start having to maintain a list again. That list is again going to be a custom things you'll have come up with instead of a standardized system.
How do you train new employees to use all of this custom stuff you've built?
Modules execute files in order based on their dependencies, so you know for sure that the stuff you depend on will have executed and will be available.
Scoping
Your solution treats everything as a standard script file. That's fine, but it means that you need to be extremely careful to not accidentally create global variables by placing them in the top-level scope of a file. This can be solved by manually adding (function(){ ... })(); around file content, but again, it's one more things you need to know to do instead of having it provided for you by the language.
Conflicts
app.component.* is something you've chosen, but there is nothing special about it, and it is global. What if you wanted to pull in a new library from Github for instance, and it also used that same name? Do you refactor your whole application to avoid conflicts?
What if you need to load two versions of a library? That has obvious downsides if it's big, but there are plenty of cases where you'll still want to trade big for non-functional. If you rely on a global object, it is now up to that library to make sure it also exposes an API like jQuery's noConflict. What if it doesn't? Do you have to add it yourself?
Encouraging smaller modules
This one may be more debatable, but I've certainly observed it within my own codebase. With modules, and the lack of boilerplate necessary to write modular code with them, developers are encouraged to look closely on how things get grouped. It is very easy to end up making "utils" files that are giant bags of functions thousands of lines long because it is easier to add to an existing file that it is to make a new one.
Dependency webs
Having explicit imports and exports makes it very clear what depends on what, which is great, but the side-effect of that is that it is much easier to think critically about dependencies. If you have a giant file with 100 helper functions, that means that if any one of those helpers needs to depend on something from another file, it needs to be loaded, even if nothing is ever using that helper function at the moment. This can easily lead to a large web of unclear dependencies, and being aware of dependencies is a huge step toward thwarting that.
Standardization
There is a lot to be said for standardization. The JavaScript community has moved heavily in the direction of reusable modules. This means that if you hope into a new codebase, you don't need to start off by figuring out how things relate to eachother. Your first step, at least in the long run, won't be to wonder whether something is AMD, CommonJS, System.register or what. By having a syntax in the language, it's one less decision to have to make.
The long and short of it is, modules offer a standard way for code to interoperate, whether that be your own code, or third-party code.
Your current process is to concatenate everything always into a single large file, only ever execute things after the whole file has loaded and you have 100% control over all code that you are executing, then you've essentially defined your own module specification based on your own assumptions about your specific codebase. That is totally fine, and no-one is forcing you to change that.
No such assumptions can be made for the general case of JavaScript code however. It is precisely the objective of modules to provide a standard in such a way as to not break existing code, but to also provide the community with a way forward. What modules offer is another approach to that, which is one that is standardized, and one that offers clearer paths for interoperability between your own code and third-party code.

JavaScript Hacking

I am trying to figure out any and all ways to prevent CSS modification and DOM modification of specific elements. I understand this might not be completely possible or that a talented developer could get around it, however, I am not so concerned about people potentially getting around it, I just want to stop newbies. In particular those using jQuery. An example would be to delete certain properties on prototype objects etc..

But why you need/want this? If you want to "protect" your code, you can use some JavaScript minifier as Google Closure Compiler or YUI compressor. They will rewrite your script and it will be difficult to read by a human. Nowadays, with tools like Firebug and Grease Monkey it's almost impossible to do what you want.

Don't use CSS or JavaScript :p Depend completely on server side checks etc.

You cannot stop anyone from messing with your javascript or your objects in the page. The way the browser is designed, your code and objects in your page are simply not protected. Everything from bookmarklets to javascript entered at a console to browser plug-ins can mess with your page and code and variables. That is the architecture of a browser.
What you can do is make things a little more difficult such that a little more work is required for some things. Here are a couple of things you could do:
Obfuscating/compressing/minimizing your code will do things like remove comments, remove whitespace, remove some linebreaks, shorten variable names, etc... That does not prevent anyone from modifying things, but does make it more work to understand and figure out.
Putting variables inside closures and not using globals. This makes it harder to directly modify variables from outside of your scripts.
Keep all important data and secrets on your server. Use ajax calls to ask the server to carry out operations using that data or secrets such that the important information is never available in the browser client.
You cannot keep anyone from modifying the DOM. There simply are no protections against that. Your code can check the DOM and refuse to operate if the DOM has been messed with in non-standard ways. But, of course, the code would then be modified to remove that check too.

If you are looking for a jquery specific solution a crude approach will involve altering the jQuery ($) function and replacing it with a custom one that delegates to the original function only if the provided selector does not match the element you want to secure.
(function(){
jQueryOrig = jQuery;
window.jQuery = window.$ = function(){
if (jQueryOrig("#secure").is(arguments[0])) {
throw new Error("Security breach");
} else return jQueryOrig.apply(this, arguments);
}
}());
Of course people using direct DOM manipulation would not be affected.
Also, if you are actually including arbitrary third party code in your production code, you should take a look at Caja ( http://code.google.com/p/google-caja/ ), which limits users to a subset of javascript capabilities. There is a good explanation regarding Caja here : http://due-diligence.typepad.com/blog/2008/04/web-20-investor.html .

This is possible but requires that the JS file to always be loaded from your server. Using observers you can lock CSS properties and using the on DOM remove/add listeners you can lock it to a parent. This will be enough to discourage most modification.
You can actually go a step further and modify core javascript functions making it nearly impossible to modify the DOM without loading the JS file locally or through a proxy. Further security can be added by doing additional domain checks to make sure the JS file is loaded from where it is supposed to be loaded from.

You can make everything in Flash. In Chrome, there's even a bug that prevents users from opening a console if the flash element has focus (not sure how exactly this works, but you can see an example at http://www.twist-cube.com or http://www.gotmilk.com). Even if users do manage to get a console open (which isn't that hard...), still about all you can do is change the shape of the element.

jQuery/JS for different pages - best way of doing this?

Apologies if this is a silly question, and I'm not even sure of the best way of wording it...
At the moment I have a site with maybe 20+ different uses of jQuery, all varying from page to page. I'm just wondering what the best way is to store this code?
Everything in one big jquery.myfunctions.js file? And check if the element exists for each statement?
Embed script tags into each individual page?
Use PHP to deliver different content into script tags kinda like the above?
Separate .js files per page? ims I don't like the sound of this at all
To be honest, I'm not even sure if jQuery does this for you, so it's okay to have multiple $('#whatever').function() loaded onto each page without any noticeable performance issues?
Any advice on this would be fantastic, probably a silly question but I want to do things the 'proper' way you know?
Thanks :-)

Personnally I like to have one file with all the things needed in it. It's better because once loaded, the browser can cache it and you don't care anymore.
As for coding, I may write pieces of code in different files, which I build as a single file for production.
This way, all your code is accessible anytime.
Nevertheless, you may include tags in your views/templates, so that you can trigger certain functions only on particular views/pages.
For example :
myObject = {
myFunctionForArticles : function(){ $('.article').each(...); },
myFunctionForCategories : function(){ ... }
};
And within the Article view :
<script type="text/javascript">
myObject.myFunctionForArticles();
</script>
Make sure your included javascript keeps very thin and general though. More than one liners calling a general function can lead to trouble. In theory it is not something you might call a best-practise. Choose what you feel is the right balance between tidyness and easiness to maintain (if you have few views, maybe you can make, along with the one big file containing all the heavy stuff, some short and specific js files, which are called only by the right view to trigger the right functions at load time ; if you have a lot of views, maybe including one-liner inline js tags will save you the burden to maintain a lot of short files).

I've recently grappled with this problem when re-starting development of a very involved web app. I decided on several patterns:
do not put inline javascript on pages in general - it prevents caching and defeats the point of separating functionality from presentation
create your own namespace - I like the DOD approach to it (http://www.dustindiaz.com/namespace-your-javascript/) So, my namespace is DG, thus all of my code is part of a single global variable called DG - which is an object, containing all of the subclasses
Create a class prototype structure, where if you're doing common things with a bit of difference between implementations
for example, logging into different sites - you're doing logins, but, some may do it differently than others - so, create a prototype class than handles generic functionality, and then implement site-specific login functionality in classes that inherit from the prototype)
Use the Yahoo Module pattern for singletons, but don't fall in love with it - it's not useful if you have more than one instance per page of a class (http://www.yuiblog.com/blog/2007/06/12/module-pattern/)
use a require/import function to do dynamic imports of javascript
this one is an optional but great. I really like doing dependencies for javascript, so I don't have to include a ton of script tags in my code, and, it really does help with performance, as most require/import frameworks load JS on demand, not at first.

My thoughts:
Never put anything on the individual
pages themselves, always use .js
files
One big file doesn't take advantage of the browser's ability to load a larger JS file as lets say 3 smaller files on 3 different concurrent connections during that critical initial page load when people enter your website
Logically group functions in
different files such as files for
validation, presentation and calculations as this makes it easier to maintain as file sizes increase
Use JSMIn (Javascript Minifier) to reduce file sizes http://www.crockford.com/javascript/jsmin.html

Is there a tool to remove unused methods in javascript?

I've got a collection of javascript files from a 3rd party, and I'd like to remove all the unused methods to get size down to a more reasonable level.
Does anyone know of a tool that does this for Javascript? At the very least give a list of unused/used methods, so I could do the manually trimming? This would be in addition to running something like the YUI Javascript compressor tool...
Otherwise my thought is to write a perl script to attempt to help me do this.

No. Because you can "use" methods in insanely dynamic ways like this.
obj[prompt("Gimme a method name.")]();

Check out JSCoverage . Generates code coverage statistics that show which lines of a program have been executed (and which have been missed).

I'd like to remove all the unused methods to get size down to a more reasonable level.
There are a couple of tools available:
npm install -g fixmyjs
fixmyjs <filename or folder>
A configurable module that uses JSHint (Github, docs) to flag functions that are unused and perform clean up as well.
I'm not sure that it removes undefined functions as opposed to flagging them. though it is a great tool for cleanup, it appears to lack compatibility with later versions of ECMAScript (more info below).
There is also the Google Closure Compiler which claims to remove dead JS but this is more of a build tool.
Updated
If you are using something like Babel, consider adding ESLint to your text editor, which can trigger a warning on unused methods and even variables and has a --fix CLI option for autofixing some errors and style issues.
I like ESLint because it contains multiple plugins for alternate libs (like React warnings if you're missing a prop), allowing you to catch bugs in advance. They have a solid ecosystem.
As an example: on my NodeJS projects, the config I use is based off of the Airbnb Style Guide.

You'll have to write a perl script. Take no notice of the nay-sayers above.
Such a tool could work with libraries that are designed to only make function calls explicitly. That means no delegates or pointers to functions would be allowed, the use of which in any case only results in unreadable "spaghetti code" and is not best practice. Even if it removes some of these hidden functions you'll discover most if not all of them in testing. The ones you dont discover will be so infrequently used that they will not be worth your time fixing them. Dont obsess with perfection. People go mad doing that.
So applying this one restriction to JavaScript (and libraries) will result in incredible reductions in page size and therefore load times, not to mention readability and maintainability. This is already the case for tools that remove unused CSS such as grunt_CSS and unCSS (see http://addyosmani.com/blog/removing-unused-css/) and which report typical reductions down to one tenth the original size.
Its a win/win situation.
Its noteworthy that all interpreters must address this issue of how to manage self modifying code. For the life of me I dont understand why people want to persist with unrestrained freedom. As noted by Triptych above Javascript functions can be called in ways that are literally "insane". This insane fexibility corrupts the fundamental doctrine of separation of code and data, enables real-time code injection, and invalidates any attempt to maintain code integrity. The result is always unreadable code that is impossible to debug and the side effect to JavaScript - removing the ability to run automatic code pre-optimisation and validation - is much much worse than any possible benefit.
AND - you'd have to feel pretty insecure about your work to want to deliberately obsficate it from both your collegues and yourself. Browser clients that do work extremely well take the "less is more" approach and the best example I've seeen to date is Microsoft Office combination of Access Web Forms paired with SharePoint Access Servcies. The productivity of having a ubiquitous heavy tightly managed runtime interpreter client and its server side clone is absolutely phenomenal.
The future of JavaScript self modifying code technologies therfore is bringing them back into line to respect the...
KISS principle of code and data: Keep It Seperate, Stupid.

Unless the library author kept track of dependencies and provided a way to download the minimal code [e.g. MooTools Core download], it will be hard to to identify 'unused' functions.
The problem is that JS is a dynamic language and there are several ways to call a function.
E.g. you may have a method like
function test()
{
//
}
You can call it like
test();
var i = 10;
var hello = i > 1 ? 'test' : 'xyz';
window[hello]();

I know this is an old question by UglifyJS2 supports removing unused code which may be what you are looking for.
Also worth noting that eslint supports an option called no-unused-vars which actually does some basic handling of detecting if functions are being used or not. It definitely detects it if you make the function anonymous and store it as a variable (but just be aware that as a variable the function declaration doesn't get hoisted immediately)
In the context of detecting unused functions, while extreme, you can consider breaking up a majority of your functions into separate modules because there are packages and tools to help detect unused modules. There is a little segment of sindreshorus's thoughts on tiny modules which might be relevant to that philosophy but that may be extreme for your use case.

Following would help:
If you have fully covered test cases, running Code Coverage tool like istanbul (https://github.com/gotwarlost/istanbul) or nyc (https://github.com/istanbuljs/nyc), would give a hint of untouched functions.
At least the above will help find the covered functions, that you may thought unused.