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Share an object instance across modules in typescript

I'm operating a bot on Wikipedia using npm mwbot, and planning to migrate to npm mwn. This is because you need a "token" to edit pages on Wikipedia, and this can expire after a while so you need to prepare your own countermeasures against this if you use mwbot, but it seems like mwn handles this issue on its own.
When you use mwn, you first need to initialize a bot instance as documented on the turotial:
const bot = await mwn.init(myUserInfo);
Then your token is stored in the bot instance and you can for example edit a page using:
const result = await bot.edit('Page title', () => {text: 'text'});
So, basically you want to share the initialized bot instance across modules. I believe it'd be easiest to declare a global variable like so:
// bot.js (main script)
const {mwn} = require('mwn');
const {my} = require('./modules/my');
(async() => {
global.mw = await mwn.init(my.userinfo);
const {t} = require('./modules/test');
t();
})();
// modules/test.js
/* global mw */
exports.t = async () => {
const content = await mw.read('Main page');
console.log(content);
return content;
};
I'm currently using JavaScript, but will hopefully migrate to TypeScript (although I'm new to it) because I feel like it'd be useful in developing some of my modules. But I'm stuck with how I should use the initialized bot instance across modules in TypeScript.
-+-- dist (<= where ts files are compiled into)
+-- src
+-- types
+-- global.d.ts
+-- bot.ts
+-- my.ts
// bot.ts
import {mwn} from 'mwn';
import {my} from './my';
(async() => {
global.mw = await mwn.init(my.userinfo);
})();
// global.d.ts
import {mwn} from 'mwn';
declare global {
// eslint-disable-next-line no-var
var mw: mwn;
}
This doesn't work and returns "Element implicitly has an 'any' type because type 'typeof globalThis' has no index signature. (at mw in global.mw)".
This is probably a naive question but any help would be appreciated.
Edit:
Thanks #CertainPerformance, that's a simple and easy approach. Actually, I once tried the same kind of an approach:
export const init = async () => {
if (typeof mw === 'undefined') {
return Promise.resolve(mw);
} else {
return mwn.init(my.userinfo).then((res) => {
mw = res;
return mw;
});
}
}
But I was like "init().then() in every module?"... don't know why I didn't come up with just exporting the initialized mwn instance.
Anyway, is it like the entry point file should be a .js file? I've been trying with a .ts file and this is one thing that's been giving me a headache. I'm using ts-node or nodemon to auto-compile .ts files, but without "type: module", "Cannot use import statement outside a module" error occurs and with that included, "TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".ts"" occurs. How do you tell a given file should be a .js or .ts file?
Edit2:
Just making a note: The error I mentioned above was caused by not having "module": "CommonJS" in my tsconfig.json, as I commented to CertainPerformance's answer below.

One of the main benefits of modules is the ability to drop dependencies on global variables. Rather than going back on that and assigning a global anyway, a better approach that happens to solve your problem as well would be to have a module that exports two functions:
One that initializes the asynchronous mwn
One that returns mwn when called
// mw.ts
import {mwn} from 'mwn';
import {my} from './my';
let mw: mwn;
export const init = async () => {
mw = await mwn.init(my.userinfo);
};
export const getMw = () => mw;
Then it can be consumed by other modules quite naturally, barely requiring any typing at all:
// modules/index.ts
// Entry point
import { init } from './mw';
import { test } from './test';
init()
.then(() => {
test();
})
// .catch(handleErrors);
// modules/test.ts
import { getMw } from './bot';
export const test = () => {
const mw = getMw();
// anything else that depends on mw
};
The above could be a reasonable approach if mw is used in many places across your app and you don't think that passing it around everywhere would be maintainable.
If you could pass it around everywhere, that would have even less of a code smell, though.
// initMw.ts
import {mwn} from 'mwn';
import {my} from './my';
export const initMw = () => mwn.init(my.userinfo);
// modules/index.ts
// Entry point
import { initMw } from './initMw';
import { test } from './test';
initMw()
.then((mw) => {
test(mw);
})
// .catch(handleErrors);
// modules/test.ts
import { mwn } from 'mwn';
export const test = (mw: mwn) => {
// anything that depends on mw
};
Initialize it once, then pass it down (synchronously) everywhere it's needed - that's the approach I'd prefer.
You could put the mwn type in a global d.ts file to avoid having to add import { mwn } from 'mwn'; to every module if you wanted. (Yes, it's somewhat of a global variable, but it's a type rather than a value, so it's arguably less of a problem.)

How can I reset a statically imported module in favour of a dynamically imported one, in mocha tests?

I have written a javascript file that provides configuration, and separately a proxy that lets me provide a fallback value if the property access was unsuccessfull
// stackUrlMap.js
export const stacks = {
'stackoverflow.com': 'StackOverflow',
'cooking.stackexchange.com': 'SeasonedAdvice',
}
// stackUrlConfig.js
import { stacks } from './stackUrlMap';
const getOrParse = parser => ({
get: (target, prop) => target?.[prop] ?? parser(prop);
})
const urlToName = url => url.split('.')[0];
export const stackUrlToNameMap = new Proxy(stacks, getOrParse(urlToName));
This was working perfectly, and I had a test written for it that passed.
import { expect } from 'chai';
import sinon from 'sinon';
import * as urlMap from './stackUrlMap';
describe('stackUrlConfig.js', function() {
let sandbox;
let stackUrlToNameMap = {};
beforeEach(async function() {
sandbox = sinon.createSandbox();
sandbox.stub(urlMap, 'stack').value({'madeup.url.com': 'Made Up Stack'});
// import here so we get the stubbed values passed through.
({ stackUrlToNameMap } = await import('./stackUrlConfig.js'))
});
it('can get an existing prop from the proxied map', function() {
const field = 'madeup.url.com';
// stub working correctly when accessed from test file
expect(urlMap.stacks[field]).to.exist();
// tests that if the proxied map can find the prop it uses that value
expect(stackUrlToNameMap[field]).to.equal('Made Up Stack');
});
})
However, now I've written code that uses stackUrlConfig.js elsewhere, that is imported by my test setup elsewhere, and the dynamically imported proxied map stackUrlToNameMap in the beforeEach of my test is not being 'respected', and the real stacks object is being used for the lookup, meaning I get this AssertionError:
AssertionError: expected 'madeup' to equal 'Made Up Stack'
If I put a console.trace in the stackUrlConfig.js, I can see it's first called before my test runs as it's imported into another file that isn't run by mocha yet.
I don't want to have to use decache (I'm not even sure it would work, I'm not using require) as seen in Re-importing modules between mocha tests if I can avoid it.
I took the code and tried to add a cache busting, like so:
const absolutePath = path.resolve(__dirname, './stackUrlConfig.js');
({ stackUrlToNameMap } = await import(`${absolutePath}?update=${Date.now()}`));
But my mocha setup did not find the resulting module.
I can't control whether this file is imported elsewhere first in my test, so can I reset mocha's reference to the module somehow?

Running unit test on JS runtime for es6 import statement

I am very new to NodeJS and JS as well. I have tried reading about resources like babel and rewire which help in resolving dependencies of ES6. But ended up being confused.
I am trying to write unit test for a JS runtime file which has import statements. The issue is that this file is a runtime file. This means that the import module only works when running in browser inside the dependent platform/application.
runtimeFile.js
import {something} from 'other-module'
function foo(){
}
export const toBeTested = {
foo
}
unitTest.js
const toBeTested = require('./runtimeFile').toBeTested
describe('some test', () => {
it('test a func', () => {
const result = tobeTested.foo();
});
});
When i try to run this unit test using mocha getting:
SyntaxError: Unexpected token {
This is for the import statement in runtimeFile.js.
So my question is around:
How do i mock the import statement
I am not sure what configuartion i need to do in order to get rid of this syntax error
I can provide more information as needed

Webpack: Undefined import during module evaluation

I came across an issue I cannot solve. Imagine we have a module
export const Do = (arg) => arg + 1;
And another module
import { Do } from './Do';
const foo = 5;
export const DoneFoo = Do(foo);
When using webpack the emited code results in Do is not a function exception (as imported Do is undefined). However if I change the code to
import { Do } from './Do';
const foo = 5;
export const GetDoneFoo = () => Do(foo);
It works fine.
It seems that webpack orders modules in an order that evaluates the file before evaluating it's dependencies.
This example is simplified. This problem occurs only in a single one large workspace and only for certain modules. My hypothesis is that dependency graph is somewhat broken, however, I have no idea how to successfully debug it and fix the reason that causes the issue.
The bundle is outputted as a library and used within a web browser (window.libraryName).

Jest mocked implementation not being called outside of test function

I have a 3rd party module I need to mock (moment.js). I want to set the implementation to the default implementation before requiring the file I'm testing. The only function I'm mocking is the default export of the module, so I assign the prototype and static members to those of the actual implementation, as well.
season.js
import moment from 'moment';
export var currentSeason = getCurrentSeason();
export function currentSeasion() {
const diff = moment().diff(/* ... */);
// ...
return /* a number */;
}
__tests__/season.js
import moment from 'moment';
jest.mock('moment');
const actualMoment = jest.requireActual('moment');
moment.mockImplementation((...args) => actualMoment(...args));
Object.assign(moment, actualMoment);
const { getCurrentSeason } = require('../season');
test('getCurrentSeason()', () => {
moment.mockReturnValue(actualMoment(/* ... */));
expect(getCurrentSeason()).toBe(1);
});
I confirmed via debugging that mockImpelementation() is being called correctly, and within the test, it's being called correctly too. However, in the initialization of currentSeason, moment() is returning undefined. When I stepped into the moment() mocked function, mockConfig.mockImpl is undefined.
Running expect(moment()).toBeUndefined() in the test file but outside of any test before the import of season.js runs the mock implementation, as well.
I can't for the life of me figure out why it's only not working in the initialization of currentSeason.

I don't know how useful this will be for anyone else, but my solution turned out to be to pull my mock code into it's own /__mocks__/moment.js file.
const actual = jest.requireActual('moment'),
moment = jest.fn((...args) => actual(...args));
export default Object.assign(moment, actual);