⚡ Lesson 05 of 30

Control Flow – if, switch

Make decisions in your programs using if/else chains, ternary expressions, and switch statements.

if / else if / else

The fundamental decision-making structure:

const score = 85;

if (score >= 90) {
  console.log("Grade: A");
} else if (score >= 80) {
  console.log("Grade: B");   // prints this
} else if (score >= 70) {
  console.log("Grade: C");
} else {
  console.log("Grade: F");
}

Ternary Operator

A compact inline conditional — perfect for simple true/false assignments:

const age = 20;
const status = age >= 18 ? "adult" : "minor";
console.log(status); // "adult"

Logical Short-circuit as Conditional

A common pattern in React and modern JS is using && to conditionally render or execute:

const isLoggedIn = true;
isLoggedIn && console.log("Welcome back!"); // prints

switch Statement

Use switch when checking one variable against many specific values. Don't forget break!

const day = "Monday";

switch (day) {
  case "Monday":
  case "Tuesday":
    console.log("Early week"); break;
  case "Friday":
    console.log("TGIF!"); break;
  default:
    console.log("Midweek");
}

Optional Chaining ?.

Access deeply nested properties without crashing if an intermediate value is null:

const user = { address: { city: "Kuala Lumpur" } };
console.log(user?.address?.city);     // "Kuala Lumpur"
console.log(user?.phone?.number);     // undefined (no error!)

← Lesson 04 🏠 Home Lesson 06 →