Classes intro

Last reviewed May 28, 2026 Content v20260528

Track mode

client_javascript

Means

In-browser JS

Reading

~1 min

Level

intermediate

This lesson

An orientation to this JavaScript lesson—scope, vocabulary, and what you will practice next.

You need a clear map of the JavaScript track so later lessons do not feel like isolated tricks.

You will apply Classes intro in contexts like: Browsers, Node.js services, edge workers, and tooling ecosystems (bundlers, test runners).

Run JavaScript in the in-browser sandbox, use the terminal output panel, and verify with MCQs. Also open the interview prep blocks.

Start here at the beginning of the javascript track before skipping ahead.

class syntax sugar over prototypes—constructors, methods, and extends for inheritance.

Basics

class User {
  constructor(name) { this.name = name; }
  greet() { return `Hi ${this.name}`; }
}

Public/private fields (#private) and static methods—see MDN for full syntax.

Q: Class vs object literal?
A: Classes help shared behavior and instanceof checks.
Q: extends?
A: Child gets parent prototype chain—call super() in constructor.

Tip: Re-run the playground code for classes-es6-intro and tweak one line before the MCQs.

Playground

Runs in your browser in a sandboxed frame. Backend runners appear when this track’s profile allows them.

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