Javascript · Conditional Statements
if/else structure
The full text of this chapter, to read or revisit. To practise, do the exercises.
▶ Do the exercisesExercise 1 — The else Branch
With
if
alone, something happens... or nothing at all. But often you want a plan B: attack OR defend, win OR lose. That's the job of
else
.
let pyrochuHP = 12;
if (pyrochuHP > 30) {
console.log("Pyrochu attacks!");
} else {
console.log("Pyrochu retreats to safety!");
}
The condition is
false
(12 is not greater than 30), so the
else
block runs. Change the HP to
50
and see the other branch run instead.
No Condition on else
else
never has its own condition. It simply means: "in all other cases". Writing
else (hp < 30)
is a syntax error.
Exercise 2 — Exactly One Branch Runs
With
if
/
else
, there are only two possible paths, and exactly one of them always runs. Never both, never zero.
let aquachuLevel = 8;
let requiredLevel = 10;
if (aquachuLevel >= requiredLevel) {
console.log("Aquachu enters the tournament!");
} else {
console.log("Aquachu needs more training...");
console.log("Missing levels: " + (requiredLevel - aquachuLevel));
}
console.log("See you at the arena!");
A branch can contain several lines. And the code after the whole
if
/
else
runs in every case.
Exercise 3 — Which Branch Runs?
What will this code print?
let florachuEnergy = 60;
if (florachuEnergy === 100) {
console.log("Full power!");
} else {
console.log("Still charging...");
}
Options
• ```Still charging...```
• ```Full power!```
• Both messages
• Nothing at all
Hint : ```===``` checks strict equality. Is 60 strictly equal to 100?
Exercise 4 — Win or Lose
Complete the battle result: if Pyrochu's score is higher than the opponent's, it wins. Otherwise, it loses.
let pyrochuScore = 340;
let opponentScore = 410;
____ (pyrochuScore ____ opponentScore) {
console.log("Pyrochu wins!");
} ____ {
console.log("Pyrochu loses...");
}
Options: if > else else < then
Hint : One keyword starts the decision, one operator means "higher than", one keyword handles all other cases.
Exercise 5 — Spot the Error
One of these
if
/
else
structures is invalid. Which one?
Options
• ```else (hp < 50) { ... }```
• ```if (hp < 50) { ... }```
• ```if (hp < 50) { ... } else { ... }```
• ```if (isReady) { ... }```
Hint : Only one of the two keywords is allowed to have its own condition in parentheses.
Exercise 6 — Type Advantage
Aquachu fights Pyrochu. Water beats fire! Complete the code so the attack is doubled when the opponent's type is
"fire"
, and normal otherwise.
let opponentType = "fire";
let attackPower = 40;
if (opponentType ____ "fire") {
console.log("Super effective! Damage: " + attackPower ____ 2);
} ____ {
console.log("Normal hit. Damage: " + attackPower);
}
Options: === * else = + if
Hint : Use the strict comparison operator, the multiplication operator, and the keyword for "in all other cases".
Exercise 7 — Match the Situation to the Branch
For this code, match each value of
hp
with what gets printed.
if (hp >= 50) {
console.log("Ready to fight");
} else {
console.log("Needs healing");
}
Items to match
• hp = 80
• hp = 50
• hp = 49
• hp = 0
Definitions
• Ready to fight
• Ready to fight
• Needs healing
• Needs healing
Exercise 8 — Boolean Variable as Condition
What will this code print?
let isSleeping = false;
if (isSleeping) {
console.log("Zzz...");
} else {
console.log("Zap is awake!");
}
Options
• ```Zap is awake!```
• ```Zzz...```
• An error, the condition has no comparison
• Nothing at all
Hint : A boolean variable is already a valid condition. Which branch runs when the condition is ```false``` ?
Exercise 9 — The Healing Center
Welcome to the Codémon Healing Center!
1. If
rockachuHP
is strictly below 40, print
"Rockachu needs healing!"
and print the missing HP (
maxHP - rockachuHP
)
2. Otherwise, print
"Rockachu is in great shape!"
Starter code
let rockachuHP = 25;
let maxHP = 100;
// Write your if/else here