Why do we need variables?
A program with a bad memory is useless
Imagine you ask a friend to remember your phone number, and every time you ask for it, they say "what number?". Useless, right? A program needs memory too. That memory is called a variable.
A variable is just a labelled box where you keep a value, so you can use it again later.
How do we make one?
let age = 25;
Read it like a sentence: "let age be 25". Now the word age holds the value 25. Anywhere you write age, JavaScript reads 25.
let name = "Aisha";
console.log(name); // shows: Aisha
console.log("Hi " + name); // shows: Hi Aisha
What is the difference between let and const?
You will see two words for making variables: let and const.
let→ a box whose value can change later.const→ a box whose value is fixed — it can never change.
let score = 0;
score = 10; // ok, score is allowed to change
const pi = 3.14;
pi = 4; // error! const cannot change
So which one should I use?
Here is a simple rule that good developers actually follow: use const by default. Only switch to let when you know the value will change (like a score going up).
Why? Because const quietly protects you. If you ever try to change something that was not meant to change, JavaScript warns you straight away, instead of letting a silent bug slip in.
One-line memory: a variable is a labelled box.
constis a locked box,letis a box you can refill.
Next, let us look at what kinds of things you can actually put inside these boxes.