✅ Prerequisite: What You Should Know in JavaScript Before Node.js

Javascript is the backbone of Node.js, to get started with Node.js, you should have a good grasp of these core JavaScript concepts:

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1. Variables and Data Types

// const, let, var
const name = "Node";
let version = 18;

• Understand string, number, boolean, null, undefined, array, and object.

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2. Functions and Arrow Functions

function greet(name) {
  return "Hello " + name;
}

const greetArrow = (name) => "Hello " + name;

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3. Objects and Arrays

const user = { name: "John", age: 30 };
const fruits = ["apple", "banana", "mango"];

• Access and manipulate values with dot/bracket notation or array indexes.

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4. Loops and Conditions

for (let i = 0; i < 5; i++) {
  console.log(i);
}

if (version > 10) {
  console.log("Modern Node.js");
}

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5. ES6+ Features (Modern JavaScript)

• Destructuring
• Template literals
• Spread/rest operator
• Promises / async-await

const { name, age } = user;

const greet = async () => {
  const response = await fetch("https://api.example.com");
  const data = await response.json();
  console.log(data);
};

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6. Modules (import/export or require)

// CommonJS (Node.js style)
const fs = require('fs');

// ES Module (Browser/Modern Node)
import fs from 'fs';

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7. Callbacks, Promises, and Async/Await

// Callback
fs.readFile("file.txt", (err, data) => {
  if (err) throw err;
  console.log(data.toString());
});

// Promise
fetch("https://api.example.com")
  .then(res => res.json())
  .then(data => console.log(data));

// Async/Await
async function getData() {
  const res = await fetch("https://api.example.com");
  const data = await res.json();
  console.log(data);
}

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8. Understanding this, Scope, and Closures

const obj = {
  name: "Node",
  greet: function () {
    console.log("Hi from " + this.name);
  }
};

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9. Events and Event-Driven Programming (important in Node.js)

const EventEmitter = require('events');
const emitter = new EventEmitter();

emitter.on('start', () => {
  console.log('Started!');
});

emitter.emit('start');

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10. Basic Error Handling

try {
  throw new Error("Something went wrong!");
} catch (err) {
  console.error(err.message);
}

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🚀 Why These Concepts Are Important for Node.js

• Node.js runs JavaScript outside the browser.
• It uses asynchronous non-blocking I/O, which makes understanding callbacks, promises, and async/await essential.
• You’ll use modules, work with files, create servers, and handle events — all built on JavaScript.

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🛠 Practice Before Moving to Node.js

If you’re not confident in the above topics:

• Practice small JavaScript apps (calculator, to-do app)