os, url & Buffers In Practice

const os = require("os");

console.log(os.platform());          // 'linux' | 'darwin' | 'win32'
console.log(os.arch());              // 'x64' | 'arm64'
console.log(os.cpus().length);       // number of logical CPU cores
console.log(os.totalmem());          // total RAM in bytes
console.log(os.freemem());           // free RAM in bytes
console.log(os.hostname());          // machine hostname
console.log(os.homedir());           // '/home/alice' or 'C:\Users\Alice'
console.log(os.tmpdir());            // '/tmp'
console.log(os.EOL);                 // '\n' on Unix, '\r\n' on Windows

const endpoint = new URL("https://api.example.com/users?page=2&limit=20");

console.log(endpoint.hostname);   // api.example.com
console.log(endpoint.pathname);   // /users
console.log(endpoint.searchParams.get("page"));   // '2'
console.log(endpoint.searchParams.get("limit"));  // '20'

// Mutate and reconstruct
endpoint.searchParams.set("page", "3");
console.log(endpoint.toString());
// https://api.example.com/users?page=3&limit=20

// urlencoded body parsing (Node.js 10+)
const params = new URLSearchParams("name=Alice&role=admin");
console.log(params.get("name"));  // Alice

// Buffers are Uint8Array subclasses — fixed-size raw memory
const buf = Buffer.alloc(8, 0);     // 8 zero bytes
buf.writeUInt32BE(1234567890, 0);   // write 4-byte big-endian int at offset 0
buf.writeUInt32LE(9876543210 >>> 0, 4); // write 4-byte little-endian int at offset 4

console.log(buf.readUInt32BE(0)); // 1234567890

// Encoding / decoding
const encoded = Buffer.from("hello world", "utf8").toString("base64");
console.log(encoded);             // aGVsbG8gd29ybGQ=
const decoded = Buffer.from(encoded, "base64").toString("utf8");
console.log(decoded);             // hello world

// Comparing and concatenating
const a = Buffer.from([1, 2, 3]);
const b = Buffer.from([4, 5, 6]);
const combined = Buffer.concat([a, b]);
console.log([...combined]); // [1, 2, 3, 4, 5, 6]