How to write a custom asynchronous module in NodeJS?

Question

JavaScript

Good day, I'm studying JS and at the moment the NodeJS platform, I'm faced with the fact that I can't understand how my modules are written correctly in Nod. Frankly speaking, there is already a mess of event-ov, callback-ov, nextTickov (setTimeout) in my head.
Everywhere, as a standard of asynchrony, they give an example of the FS module:

var fs = require('fs');
fs.readFile('name.txt', function (err, data) {
});

We connected the fs module, called its method and passed a variable and a callback to it.
The problem is that they don’t write anywhere about what happens inside. By googling and studying, I came up with this code:

// my custom module
function MyModule(something, callback){
    if(something === 'OK'){        // Обрабатываем как-то something и передаем дальше
      process.nextTick( сallback(null, something));
    } else {
       process.nextTick( callback('Error')); 
    };
};
module.exports = MyModule;

Well, using it like the fs module:

var MyModule = require('MyModule');
MyModule('something', function( err, value ) {
   if(err) console.log('Вай-вай, беда!')
   // ну а тут делаем еще что-то с value
});

Well, now the question itself, will it be asynchronous and generally work, or have I wandered into the wrong steppe at all?
Thanks to.
PS. the idea to hang events on everything that is possible is also spinning in my head, but so far I can’t arrange it coherently as I see it. If it's not difficult for anyone, throw a code like this at events or a link to an sensible article. Thanks again.

Answer 1

So you can see how the same fs module is written: https://github.com/joyent/node/blob/master/lib/fs.js
How to write asynchronous functions You found the code is normal, but the asynchronous module is nonsense , here is fs module synchronous or asynchronous? After all, it has fs.readFile and fs.readFileSync. A module can contain both synchronous and asynchronous code; in general, only I/O is usually solved asynchronously in a node: working with files, network, database. All other code remains synchronous. It seems that you have not yet fully mastered the node, but already want to make your own modules. I recommend that you read the sources of good modules before that, for example, these small and well-written ones:
https://www.npmjs.com/package/mkdirp
https://www.npmjs.com/package/ncp
https://www.npmjs.com/package/colors
I advise you to go through nodeschool.io/ru and practice using modules, and then make your own. Also, be sure to master the async library: https://github.com/caolan/async and see what EventEmitter is https://nodejs.org/api/events.html And of course, read the source code of the node and other modules. Articles to google or dig on Habré should not be a problem.