Writing express.js app. Where do helper methods go?

Question

So I have started with express.js - my first JS web dev framework. I didn't make anything small, but started a bigger project. I'm learning, and building at the same time.

Coming from a Python/Flask background, express seems very complicated.

Like in python, if I want a helper method, I can just put it on top of the file, or in a new module, and import it. Super easy. But in node/express, things are async, and everything is in exports or module.exports (??). Where do helper methods go? How do I call them with callbacks?

In another question I asked, I was doing the same kind of computation multiple times. In Python, I would write a method (with if statements and parameters), and call it multiple times, using a for.. in... loop. The code I have right now is very redundant.

How do I do it in express? What are best practices for writing express code?

Answer 1

It really depends of what your helper is doing. If it operates with data which is passed as a parameter to it then you may save it in an external module and use require to access it.

// helpers/FormatString.js
module.exports = function(str) {
   return str.toUpperCase();
}

// app.js
var formatter = require("./helpers/FormatString");

However, if you need to modify the request or the response object then I'll suggest to define it as a middleware. I.e.:

app.use(function(req, res, next) {
   // ... do your stuff here
});