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Is there a way to access/modify the "Execution Context" of a Node module/function

I understand the scoping rules of Node/JavaScript, and from, for example, Understanding Execution Context and Execution Stack in Javascript, I think I understand the principle of how Execution Contexts work: the question is can you actually get access to them?
From an answer to the 2015 question How can I get the execution context of a javascript function inside V8 engine (involving (ab)using (new Error()).stack), and the answer to the 2018 question How can we get the execution context of a function?, I suspect the answer is "no" but just in case things have changed: is it possible to access/modify the Execution Context of a Node module/function?
(I'm very aware this screams either XY Problem or a desire to abuse Node/JavaScript: hopefully the Background section below will provide more context, and – if there's a different way of achieving what I want – that will work as well.)
In a nutshell, I want to achieve something like:
sharedVar = 1 ;
anotherModule.someFunction() ;
console.log( sharedVar ) ; // Where 'sharedVar' has changed value
Having a function in a different module being able to change variables in its caller's scope at will seems the definition of "A Dangerous Thing™", so – if it's possible at all – I expect it would need to be more like:
sharedVar = 1 ;
anotherModule.hereIsMyExecutionContext( SOMETHING ) ;
anotherModule.someFunction() ;
console.log( sharedVar ) ; // Where 'sharedVar' has changed value
and anotherModule would be something like:
let otherExecutionContext ;
function hereIsMyExecutionContext( anExecutionContext ) {
otherExecutionContext = anExecutionContext ;
}
function someFunction() {
//do something else
otherExecutionContext.sharedVar = 42 ;
}
and the question becomes what (if anything) can I replace SOMETHING with?
Notes / Things That Don't Work (for me)
You shouldn't be trying to do this! I realize what I'm trying to achieve isn't "clean" code. The use-case is very specific, where brevity (particularly in the code whose value I want changing) is paramount. It is not "production" code where the danger of forgotten, unexpected side-effects matters.
Returning a new value from the function. In my real use-case, there would be several variables that I would like someFunction() to be able to alter. Having to do { var1, var2, ... varN } = anotherModule.someFunction() would be both inconvenient and distracting (while the function might change some of these variables' values, it is not the main purpose of the function).
Have the variables members of anotherModule. While using anotherModule.sharedVar would be the clean, encapsulated way of doing things, I'd really prefer not to have to use the module name every time: not only is it more typing, but it distracts from what the code that would be using these variables is really doing.
Use the global scope. If I wasn't using "use strict";, it would be possible to have sharedVar on the global object and freely accessible by both bits of code. As I am using strict-mode (and don't want to change that), I'd need to use global.sharedVar which has the same "cumbersomeness" as attaching it to anotherModule.
Use import. It looks like using import { sharedVar } from anotherModule allows "live" sharing of the variables I want between the two modules. However, by using import, the module using the shared variable has to be an ES Module (not a CommonJS Module), and cannot be loaded dynamically using require() (as I also need it to be). Loading it dynamically the ESM way (using import() as a function returning a promise) appears to work, but repeated loadings come from a cache. According to this answer to How to reimport module with ES6 import, there isn't a "clean" way of clearing that cache (cf. delete require.cache[] that works with CommonJS modules). If there is a clean way of invalidating a cached ESM loaded through import(), please feel free to add an answer to that question (and a comment here, please), although the current Node JS docs on ESMs don't mention one, so I'm not hopeful :-(
Background
In early December, a random question on SO alerted me to the Advent of Code website, where a different programming problem is revealed everyday, and I decided to have a go using Node. The first couple of problems I tackled using standalone JS files, at which point I realized that there was a lot of common code being copy-pasted between each file. In parallel with solving the puzzles, I decided to create a "framework" program to coordinate them, and to provide as much of the common code as possible. One goal in creating the framework was that the individual "solution" files should be as "lean" as possible: they should contain the absolute minimum code over that needed to solve the problem.
One of the features of the framework relevant to this question is that it reloads (currently using require()) the selected solution file each time, so that I can work on the solution without re-running the framework... this is why switching to import and ES Modules has drawbacks, as I cannot (cleanly) invalidate the cached solution module.
The other relevant feature is that the framework provides aoc.print(...) and aoc.trace(...) functions. These format and print their arguments: the first all the time; the second conditionally, depending on whether the solution is being run normally or in "trace" mode. The latter is little more than:
function trace( ... ) {
if( traceMode ) {
print( ... )
}
}
Each problem has two sets of inputs: an "example" input, for which expected answers are provided, and the "real" input (which tends to be larger and more involved). The framework would typically run the example input with tracing enabled (so I could check the "inner workings") and run the "real" input with tracing disabled (because it would produce too much output). For most problems, this was fine: the time "wasted" preparing the parameters for the call, and then making the call to aoc.trace() only to find there was nothing to do, was negligible. However, for one solution in particular (involving 10 million iterations), the difference was significant: nearly 30s when making the ignored trace; under a second if they calls were commented-out, or I "short-circuited" the trace-mode decision by using the following construct:
TRACE && aoc.print( ... )
where TRACE is set to true/false as appropriate. My "problem" is that TRACE doesn't track the trace mode in the framework: I have to set it manually. I could, of course, use aoc.traceMode && aoc.print( ... ), but as discussed above, this is more to type than I'd like and makes the solution's code more "cluttered" than I'd ideally want (I freely admit these are somewhat trivial reasons...)

One of the features of the framework relevant to this question is that it reloads the selected solution file each time
This is key. You should load not leave the loading, parsing and execution to require, where you cannot control it. Instead, load the file as text, do nefarious things to the code, then evaluate it.
The evaluation can be done with eval, new Function, the vm module, or by messing with the module system.
The nefarious things I was referring to would most easily be prefixing the code by some "implicit imports", whether you do that by require, import or just const TRACE = true;. But you can also do any other kind of preprocessing, such as macro replacements, where you might simply remove lines that contain trace(…);.

Looks like you're heading the wrong way. The Execution Context isn't meant to be accessible by the user code.
An option is to make a class and pass its instances around different modules for your purpose. JS objects exist in the heap and can be accessed anywhere as long as you have its reference, so you can control it at will.

Is it ok to declare an object to be equal to itself in Javascript for the sake of refactoring a large project

I'm working on a very large javascript web app that doesn't really have a method to it. There seems to be an attempt to declare everything as part of a master object called "app". The original program existed as a single app.js file over 300k lines of code where the following was declared:
var app = {};
Beyond that everything in the app is written as such.
app.somefunction = function(args, callback) {
some code
};
This apparently allowed for the author to handily use Eclipse IDE "outline", which I confess I have started to enjoy having, never previously having been an IDE user I'm becoming a convert to the niceties they provide.
My question is, as I work on a phased refactor of this huge codebase, potentially trying to merge it into some sort of more established framework perhaps using something like require.js, is it OK to split the "app.js" up into smaller files and for the sake of sanity to be able to use the IDE outline declare app to be equal to itself in each one.
app = app;
I've tested this, it works from what I can tell and it allows the IDE to add all the subsequent functions to the outline window while making the project a little more manageable while I learn what it is actually doing. Are there any drawbacks to doing this? I imagine some async loading issues might occur; this could possibly add to client side overhead; or is this perfectly acceptable?
I realize that this is sort of a code philosophy question, but the simple Q&A would be, what effect would app=app; have?

There's no problem doing that.
In fact, this is pretty common code:
var app = app || {};
to initialize a variable only if it doesn't already have a value. In the case where it does already have a value, it will be exactly equivalent to your app = app;
This technique can also be useful for initializing a large object like you have in multiple chunks, allowing you to reorder and omit chunks at will, while being sure that no chunk is going to wipe another's initializations by doing var app = {}

Dependency Injection vs. Managed Dependencies vs. Global Object

I'm working within a Javascript + BackboneJS (an MVC framework) + RequireJS framework, but this question is somewhat OO generic.
Let me start by explaining that in Backbone, your Views are a mix of traditional Views and Controllers, and your HTML Templates are the traditional MVC Views
Been racking my head about this for a while and I'm not sure what the right/pragmatic approach should be.
I have a User object that contains user preferences (like unit system, language selection, anything else) that a lot of code depends on.
Some of my Views do most of the work without the use of templates (by using 3rd party libs, like Mapping and Graphing libs), and as such they have a dependency on the User object to take care of unit conversion, for example. I'm currently using RequireJS to manage that dependency without breaking encapsulation too much.
Some of my Views do very little work themselves, and only pass on Model data to my templating engine / templates, which do the work and DO have a dependency on the User object, again, for things like units conversion. The only way to pass this dependency into the template is by injecting it into the Model, and passing the model into the template engine.
My question is, how to best handle such a widely needed dependency?
- Create an App-wide reference/global object that is accessible everywhere? (YUK)
- Use RequireJS managed dependencies, even though it's generally only recommended to use managed dependency loading for class/object definitions rather than concrete objects.
- Or, only ever use dependency injection, and manually pass that dependency into everything that needs it?

From a purely technical point of view, I would argue that commutable globals (globals that may change), especially in javascript, are dangerous and wrong. Especially since javascript is full of parts of code that get executed asynchronously. Consider the following code:
window.loggedinuser = Users.get("Paul");
addSomeStuffToLoggedinUser();
window.loggedinuser = Users.get("Sam");
doSomeOtherStuffToLoggedinUser();
Now if addSomeStuffToLoggedinUser() executes asynchronously somewhere (e.g. it does an ajax call, and then another ajax call when the first one finishes), it may very well be adding stuff to the new loggedinuser ("Sam"), by the time it gets to the second ajax call. Clearly not what you want.
Having said that, I'm even less of a supporter of having some user object that we hand around all the time from function to function, ad infinitum.
Personally, having to choose between these two evils, I would choose a global scope for things that "very rarely change" --- unless perhaps I was building a nuclear powerstation or something. So, I tend to make the logged in user available globally in my app, taking the risk that if somehow for some reason some call runs very late, and I have a situation where one user logs out and directly the other one logs in, something strange may happen. (then again, if a meteor crashes into the datacenter that hosts my app, something strange may happen as well... I'm not protecting against that either). Actually a possible solution would be to reload the whole app as soon as someone logs out.
So, I guess it all depends on your app. One thing that makes it better (and makes you feel like you're still getting some OO karma points) is to hide your data in some namespaced singleton:
var myuser = MyApp.domain.LoggedinDomain.getLoggedinUser();
doSomethingCoolWith(myuser);
in stead of
doSomethingCoolWith(window.loggedinuser);
although it's pretty much the same thing in the end...

I think you already answered your own question, you just want someone else to say it for you : ) Use DI, but you aren't really "manually" passing that dependency into everything since you need to reference it to use it anyways.

Considering the TDD approach, how would you test this? DI is best for a new project, but JS gives you flexible options to deal with concrete global dependencies when testing, ie: context construction. Going way back, Yahoo laid out a module pattern where all modules were loosely coupled and not dependent on each other, but that it was ok to have global context. That global context can make your app construction more pragmatic for things that are constantly reused. Its just that you need to apply that judiciously/sparingly and there need be very strong cases for those things being dynamic.

JSLint fails file due to undefined variable

I have just started putting JSLint into my build pipeline and it has been great. Although it has pointed out something in most of my files that is not an error as such, although it will see it as one. I have changed my constructor to now take an instance of this object so the tests pass, however I am not sure if I really should, as in all other major languages I would not need to do this.
I will have to add some more context to this, for it to make any sense so here goes.
I have the closest thing I can get to an Enum in javascript which is basically a globally scoped JSON style variable with a load of constants, it is used to describe event types so rather than every class that wants to raise/listen to events having to put hard coded strings, it can just use a constant from this enum variable. As I just mentioned I have these classes that make use of this static enum, but they just make use of the global version of this variable, not a local instance passed through the constructor, and this is where my problems begin, as in the actual app I know for a fact that the enum file will included which will make it globally accessible. However JSLint has no context of this, so it only sees an individual file without worrying about external dependencies, as it deems these to be bad, which in any other language would be true, but in JS you cannot achieve the same thing without having global variables (to my knowledge).
As I said originally, I have now added this enum to the constructor to let JSLint pass the files, however it just feels a bit wrong passing it in, but maybe this is because I am thinking about it as a regular developer and not a javascript developer...
Now should I stick to this, and pass it through the constructor, and just mock it in my tests, or should I take the approach that it should always be there?
I am sure this will be down to peoples personal opinions, but it would be nice to know if I am being an idiot and should just keep each file as its own silo, or if there is a way for me to have my cake and eat it.

I found that JSLint supports a comment to tell it of global variables:
/*globals myGlobal*/
I have decided to just use my enum as a global and get on with the more important things.

JavascriptLint greatly improves on JSLint in this respect, as it allows you to define inter-file dependencies:
If a script references a variable, function, or object from another script, you will need to add a /*jsl:import PathToOtherScript*/ comment in your script. This tells JavaScript Lint to check for items declared in the other script. Relative paths are resolved based on the path of the current script.
See: http://javascriptlint.com/docs/index.htm

A question about referencing functions in Javascript

The problem: I have a jQuery heavy page that has a built in admin interface. The admin functions only trigger when an admin variable is set. These functions require a second library to work properly and the second file is only included if the user is an admin when the page is first created. The functions will never trigger for normal users and normal users do not get the include for the second library.
Is it bad to reference a function does not exist in the files currently included even if that function can never be called? (does that make sense :)
Pseudocode:
header: (notice that admin.js is not included)
<script type="text/javascript" src="script.js"></script>
<script type="text/javascript" src="user.js"></script>
script.js: (admin functions referenced but can't be executed)
admin = false; // Assume this
$(".something").dblclick(function(){
if(admin)
adminstuff(); // Implemented in admin.js (not included)
else
userstuff();
});
Ideas:
I suppose two separate files for users and admins could be used but I feel that would be an overly complicated solution (don't want to maintain two large files with only a few lines of difference). The only reason I include a reference to the admin function in this file is I need to attach it to page elements that get refreshed as a part of the script. When jQuery refreshes the page I need to reattach function to interactive elements.
The Question:
I want to keep things very simple and not have to include file I don't have to if they will not be used by the user. Is this a good way to do this or should I be going another route?

The code should operate without error, since the admin functions without implementation will not be called. The only thing that is really being wasted is bandwidth to transmit the admin code that is not used.
However, let me caution against security through obscurity. If the user were to view this code and see that there are admin functions that they cannot access, they might get curious and try to download the "admin.js" file and see what these functions do. If your only block to keeping admin functions from being performed is to stop including the file, then some crafty user will probably quickly find a way to call the admin functions when they should not be able to.
If you already do server side authentication/permissions checking for the admin function calls just ignore my previous paragraph :-)

Personally, I would bind (or re-bind) the event in admin.js:
$(function() {
$(".something").dblclick(function(){
adminstuff();
});
});
function adminstuff()
{
// ...
}
That way, the adminstuff() call and the function will not be visible to "normal" users.

Good question. It shouldn't cause any JavaScript problems.
Other things to consider: you are potentially exposing your admin capabilities to the world when you do this, which might be useful to hackers. That's probably not much of a concern, but it is something to be aware of.
See also:
Why can I use a function before it’s defined in Javascript?

I don't think it matters. If it makes you feel better, you can make an empty stub function.

I don't think there's a dogmatic answer to this in my opinion. What you're doing is...creative. If you're not comfortable with it, that could be a sign to consider other options. But if you're even less comfortable with those then that could be a sign this is the right thing (or maybe the least wrong thing) to do. Ultimately you could mitigate the confusion by commenting the heck out of that line. I wouldn't let yourself get religious over best practices. Just be willing to stand by your choice. You've justified it to me, anyway.

Javascript is dynamic - it shouldn't care if the functions aren't defined.
If you put your admin functions in a namespace object (probably a good practice anyway), you have a couple of options.
Check for the existence of the function in the admin object
Check for the existence of the admin object (possibly replacing your flag)
Have an operations object instead, where the admin file replaces select functions when it loads. (Even better, use prototypical inheritance to hide them.)

I think you should be wary that you are setting yourself up for massive security issues. It is pretty trivial in firebug to change a variable such as admin to "true", and seeing as admin.js is publically accessible, its not enough to simple not include it on the page, as it is also simple to add another script tag to the page with firebug. A moderately knowledgeable user could easily give themselves admin rights in this scenario. I don't think you should ever rely on a purely client side security model.