Javascript · Variables
Constants
The full text of this chapter, to read or revisit. To practise, do the exercises.
▶ Do the exercisesExercise 1 — Constants with const
Sometimes you want a variable that never changes. For this, use
const
(short for "constant"):
const maxCodemonInTeam = 6;
const gameName = "Codémon Adventure";
console.log(maxCodemonInTeam);
console.log(gameName);
These values won't change during your program - they're constant!
Exercise 2 — When to Use const vs let
Once you create a
const
, you cannot change it. Try uncommenting the last line and run the code:
App limitation
On mobile, the following example won't show an error message when you try to reassign a
const
. However, if you run the same code on a computer, you'll see an error in the console.
const starter = "Aquachu";
console.log(starter);
// starter = "Pyrochu"; // Uncomment this line to see the error!
Now let's compare
const
and
let
:
const vs let
const
→ Values that never change
• Game settings:
const maxLevel = 100;
• Fixed data:
const gameName = "Codémon";
let
→ Values that will change
• Counters:
let score = 0;
• Health:
let hp = 100;
Exercise 3 — Which Keyword Should You Use?
What happens if you try to change a
const
variable?
Options
• JavaScript throws an error
• The value changes normally
• It displays a warning but works
• Nothing happens, the value stays the same
Hint : Remember: ```const``` exists to protect a value from being modified. How would JavaScript react to enforce that protection?
Exercise 4 — Which Keyword Should You Use?
You're storing the name of your game, which will never change. Which should you use?
Options
• ```const gameName = "Codémon";```
• ```let gameName = "Codémon";```
• ```var gameName = "Codémon";```
• All are equally good
Hint : If the value never changes, use ```const```. If it will change, use ```let```!
Exercise 5 — Create a Constant
Complete this code to create a constant for the maximum team size:
____ ____ ____ ____ ____
Options: const maxTeamSize = 6 ; let var
Hint : If the value never changes, use ```const```. If it will change, use ```let```!
Exercise 6 — const or let?
You're tracking a Codémon's health that will decrease during battles. Which should you use?
Options
• ```let health = 100;```
• ```const health = 100;```
• ```var health = 100;```
• It doesn't matter
Hint : Health will change during battles, so you need a variable that can be updated!
Exercise 7 — Build Your Team
Create a Codémon team management system!
1. Create a
const
called
teamName
with your team's name
2. Create a
const
called
maxTeamSize
set to
6
3. Create a
let
variable
currentTeamSize
starting at
1
(just your starter)
4. Add 2 more Codémon to your team (change
currentTeamSize
to
3
)
5. Display the team name, max size, and current size
Starter code
// Build your team here