Conditionals

Programs get interesting when they make decisions. In this lesson you'll write code that prints different output depending on a value.

What you'll learn

• Write if / else if / else to branch on a condition
• Use comparison operators (===, <, >, <=, >=, !==)
• Combine conditions with && (and), || (or), ! (not)

Instructions

Given a variable age set to 30, print exactly one of:

• child — when age < 13
• teen — when age is between 13 and 17 (inclusive)
• adult — when age >= 18

Your code must use all three of if, else if, and else.

Key concepts

Branching with if / else if / else

const score = 72;
if (score >= 90) {
  console.log("A");
} else if (score >= 60) {
  console.log("B");
} else {
  console.log("C");
}

Each branch checks its condition in order. As soon as one is true, that block runs and the rest are skipped. else is the fallback when none of the earlier checks match.

Comparison operators

| Operator | Meaning | | --- | --- | | === | equal (strict) | | !== | not equal | | < <= | less than / ≤ | | > >= | greater than / ≥ |

Prefer === over == — === compares without type coercion, which avoids a family of bugs like "0" == 0 being true.

Combining conditions

if (age >= 13 && age <= 17) console.log("teen");
if (isWeekend || isHoliday) console.log("no school");
if (!isLoggedIn) console.log("please log in");

• && — both sides must be true
• || — either side must be true
• ! — flip a boolean

Hints

1. Start with if (age < 13).
2. Next comes else if (age < 18) — the age range check piggybacks on the previous one failing.
3. The final else covers everything else.