Javascript · Variables
What are variables?
The full text of this chapter, to read or revisit. To practise, do the exercises.
▶ Do the exercisesExercise 1 — What Are Variables?
Variables are containers that store values. Think of them as labeled boxes where you can keep information.
let starterName = "Aquachu";
console.log(starterName);
Here,
starterName
is a variable storing the text
"Aquachu"
. We can use it throughout our code!
Exercise 2 — Declaring Variables with let
To create a variable in JavaScript, we use the keyword
let
:
let codemonType = "water";
let niveauPuissance = 75;
Variables are named 'variables' because their value can change! Look at that:
let health = 100;
console.log(health);
health = 80; // Changed!
console.log(health);
Here, we initially set the variable
health
to 100, then later changed it to 80.
Exercise 3 — What About var?
Another keyword to create variables is
var
. You might see it in older JavaScript code:
var oldWay = "This is outdated";
let modernWay = "This is better!";
I advise you to always use
let
instead of
var
. Why?
-
var
has confusing scoping rules
-
let
is more predictable and safer
- Modern JavaScript uses
let
Exercise 4 — Which Keyword to Use?
Which keyword should you use to declare a variable in modern JavaScript?
Options
• ```let```
• ```var```
• ```variable```
• ```define```
Hint : Use the modern way! Avoid ```var```.
Exercise 5 — Create Your First Variable
Complete this code to create a variable:
____ ____ ____ ____ ____
Options: let = var define starterName set "Pyrochu" ;
Hint : Use ```let``` to declare, then the variable name, ```=```, and the value.
Exercise 6 — Changing a Variable's Value
You created a variable like this:
let codemonLevel = 5;
Now your Codémon leveled up! Which code correctly changes its level to 6?
Options
• ```codemonLevel = 6;```
• ```let codemonLevel = 6;```
• ```codemonLevel == 6;```
• ```var codemonLevel = 6;```
Hint : To change a variable's value, just use its name and ```=```. Don't use ```let``` again - that would try to create a new variable with the same name!
Exercise 7 — Battle Damage!
Your Aquachu starts with 100 HP, but takes 25 damage in battle. Complete the code:
____ health ____ 100;
console.log(health);
____ ____ 75;
console.log(health);
Options: let = = health var == set
Exercise 8 — Match Code and Result
Match each code snippet with what it displays:
Items to match
• let power = 50;
console.log(power);
• let power = 50;
power = 75;
console.log(power);
• let name = "Aquachu";
console.log(name);
• let type = "water";
type = "fire";
console.log(type);
Definitions
• Displays: 50
• Displays: 75
• Displays: Aquachu
• Displays: fire
Exercise 9 — Create Your Codémon
Time to create your own Codémon! Write code to:
1. Create a variable
codemonName
with your favorite starter (Aquachu, Pyrochu, or Florachu)
2. Create a variable
hp
starting at
100
3. Your Codémon takes 25 damage in battle (change
hp
to
75
)
4. Display both the name and new HP
Starter code
// Create your Codémon here