Syntax & Basics 🧱

JavaScript basics are the building blocks for every app—from quick scripts to large frontends.

1) Variables & Declarations 🏷️

• let → block-scoped, reassignable (use for most variables).
• const → block-scoped, cannot be reassigned (protects constants/refs).
• var → function-scoped, hoisted; avoid unless maintaining legacy code.

let score = 0;
const API_URL = "https://api.example.com";
var legacyFlag = true;

2) Data Types 🧪

• Primitives: string, number, bigint, boolean, null, undefined, symbol.
• Reference types: object, array, function, Date, etc.
• Use typeof to inspect values.

typeof 42; // "number"
typeof null; // "object" (historical quirk)

3) Operators ⚙️

• Arithmetic: +, -, *, /, %, **.
• Assignment: =, +=, -=.
• Comparison: === (strict equality), !==, <, >.
• Logical: &&, ||, ??, !.
• Optional chaining: obj?.nested?.value avoids crashes if missing.

4) Conditionals 🔀

if (score > 10) {
  celebrate();
} else if (score > 5) {
  cheer();
} else {
  keepTrying();
}

• Ternary: const status = score > 10 ? "winner" : "player";
• Switch for multiple discrete values:

switch (command) {
  case "start": start(); break;
  case "stop": stop(); break;
  default: help();
}

5) Loops 🔁

• for loop when you know the count.

for (let i = 0; i < 3; i++) {
  console.log(i);
}

• while / do...while for condition-based loops.
• for...of iterates over arrays/iterables; for...in iterates object keys.

for (const user of users) {
  greet(user);
}

Key Takeaways ✅

• Prefer const/let; reserve var for legacy scopes.
• Know the difference between primitives and references.
• Use strict equality (===) to avoid surprise type coercion.
• Loops and conditionals combine to control program flow.

Recap 🔄

Mastering declarations, data types, operators, branching, and looping gives you the language grammar you’ll reuse everywhere else in JavaScript.