JavaScript Get Started

To start writing JavaScript, you need exactly two things:

1. A JavaScript engine — every modern browser already has one (Chrome's V8, Firefox's SpiderMonkey, Safari's JavaScriptCore). For terminal scripts you also want Node.js.
2. A text editor or IDE — VS Code, WebStorm, Sublime Text, or even Notepad.

Good news: you almost certainly already have a JavaScript engine — your browser. You can write your first JS line of code in the next 10 seconds.

Verify your install:

bash
node --version
npm --version

You should see something like:

v20.11.0
10.2.4

Step 1. Create a file hello.js:

javascript Run in compiler
console.log("Hello, Codekilla!");

Step 2. Run it (no compilation step needed — JS is interpreted):

bash
node hello.js

Hello, Codekilla!

That's it. No javac, no g++, no make. Edit → run.

• Node read hello.js from disk.
• The V8 engine parsed your source into an AST (Abstract Syntax Tree).
• V8 JIT-compiled the hot bytecode to native machine code on the fly.
• It executed console.log, which writes to stdout (the terminal).

You don't compile JS ahead of time the way you do with C++ or Java — the engine does it lazily, the moment your code runs.

Same language, different host environment. The core syntax is identical.

A safe default for learning:

bash
node --watch hello.js

1. Install VS Code.
2. Add the JavaScript and TypeScript Nightly extension (built-in support is already great).
3. Add ESLint + Prettier for linting + formatting.
4. Add Code Runner (optional, gives you a one-click ▶ Run button).
5. Open your folder, create hello.js, hit ▶ — you're coding.

1. Open any web page (yes, this one works).
2. Press F12 (Windows / Linux) or Cmd + Option + I (macOS).
3. Click the Console tab.
4. Type 1 + 1 and press Enter — you'll see 2.
5. Try console.log("hi") — instant feedback.

This REPL playground is the single fastest way to experiment.

Don't want to install anything? Use Codekilla's online JavaScript compiler — write code in the browser, click Run, see output. Perfect for learning on the go.

Real JS projects use npm (Node Package Manager) — fetches libraries, runs scripts, manages versions:

bash
npm init -y                  # create package.json
npm install chalk            # add a dependency
npm run dev                  # run a script defined in package.json

The npm registry has 3 million+ packages — the largest on Earth. You'll meet yarn and pnpm later; for now, plain npm is fine.

• Running node hello instead of node hello.js — Node needs the full filename.
• Forgetting console.log() — typing "hello" alone in a .js file produces no output (unlike a REPL).
• Mixing require (CommonJS) and import (ESM) in the same project without setting "type": "module" in package.json.
• Running npm install in the wrong folder — packages land in the current directory's node_modules.
• Trusting a globally-installed CLI — global versions drift. Prefer npx <tool> so it pulls the project's pinned copy.

1. First script — Create hello.js with console.log("Hi, " + your_name) and run it via node hello.js. Hint: replace your_name with a string literal.
2. REPL exploration — Open the Node REPL (node with no args) and try [1, 2, 3].map(x => x * 2). Hint: arrow functions transform array elements.
3. First package — Run npm init -y, then npm install chalk, then write a script that prints chalk.green("✓ success"). Hint: use import chalk from "chalk" and add "type": "module" to package.json.

💡 Think Like a Programmer: Prefer npx <tool> over npm install -g <tool>. Global installs drift over time and create "works on my machine" bugs. npx always runs the project's pinned version.