Lesson · Chapter: Conditions+10 XP for reading
Making Decisions
Programs can make choices! Use if to run code only when something is true.
Where you'll use this
Ride gates check your age, logins check your password, games check if you're out of lives — every decision in software is a condition.
The if Statement
javascript
let age = 15;
if (age >= 12) {
console.log("You can ride the roller coaster!");
}
Output
Press Run to see the output.
The condition goes in parentheses ( ), and the code to run goes between curly braces { }. If the condition is true, the code inside the braces runs. If not, it's skipped.
Comparison Operators
| Operator | Meaning |
|---|---|
=== | Equal to |
!== | Not equal to |
< | Less than |
> | Greater than |
<= | Less than or equal |
>= | Greater than or equal |
Always use the triple === to compare — a single = stores a value instead of comparing!
if / else
Use else for when the condition is false:
javascript
let age = 8;
if (age >= 12) {
console.log("You can ride!");
} else {
console.log("Too young!");
}
Output
Press Run to see the output.
Output:
Too young!
if / else if / else
Use else if to check multiple conditions:
javascript
let score = 85;
if (score >= 90) {
console.log("A");
} else if (score >= 80) {
console.log("B");
} else if (score >= 70) {
console.log("C");
} else {
console.log("F");
}
Output
Press Run to see the output.
Output:
B
Boolean Logic
Combine conditions with && (and), || (or), and ! (not):
javascript
let age = 10;
let hasTicket = true;
if (age >= 8 && hasTicket) {
console.log("Enjoy the show!");
}
Output
Press Run to see the output.
Don't Forget the Parentheses and Braces!
The condition must be wrapped in parentheses, and the body goes in braces:
javascript
// Correct
if (age >= 12) {
console.log("Welcome!");
}
// Wrong — will cause an error!
if age >= 12
console.log("Welcome!");
Output
Press Run to see the output.
Did you know?
Pac-Man's four ghosts each run different if-rules: one chases you directly, one aims ahead of you, one is unpredictable. Every game "AI" you've ever played against is conditions underneath.
Check yourself
Pause & predict — what will this print?
let age = 10;
let hasTicket = false;
if (age >= 8 || hasTicket) {
console.log("Welcome in!");
}