====== Modules in Node.js ======


==== Built-in Modules ====


Node.js comes with several built-in modules like ''fs'', ''http'', ''path'', and ''os''.

Example using the ''fs'' module to read a file:

<code>
const fs = require("fs");
fs.readFile("example.txt", "utf8", (err, data) => {
  if (err) {
    console.error(err);
    return;
  }
  console.log(data);
});
</code>

==== Creating Custom Modules ====


Create ''math.js'':

<code>
exports.add = (a, b) => a + b;
exports.subtract = (a, b) => a - b;
</code>

Use it in ''app.js'':

<code>
const math = require("./math");
console.log(math.add(5, 3));
</code>