A Node module is simply a Javascript file. Reference functions (and anything else) that might be useful to outside code to exports, as follows:
// library1.js
function function1a() {
return "hello from 1a";
}
exports.function1a = function1a;
We now have a module that can be required by another file. Back in our main app, let's use it:
// app.js
const library1 = require('./library1'); // Require it
const function1a = library1.function1a; // Unpack it
let s = function1a(); // Use it
console.log(s);
Note how it was not necessary to use the .js suffix. We’ll discuss how Node resolves paths shortly.
Let's make our library a little bigger, growing it to three functions, as shown:
// library1.js
exports.function1a = () => "hello from 1a";
exports.function1b = () => "hello from 1b";
exports.function1c = () => ...