Variables — let and const

A variable is a named box

• A variable stores a value and gives it a name, so you can use it again later.
• let makes a box you can change.
• const makes a box that must stay the same (a constant).

let age = 15;          // a value that may change
const name = "Ada";    // a value that won't
console.log(name, age);   // → Ada 15

Change a let with a new value

• Assign again — count = count + 1 — to update a let.
• count++ is a handy shortcut for "add 1 to count".

let count = 0;
count = count + 1;
count++;
console.log(count);   // → 2

Watch out

• A const cannot be reassigned: const x = 1; x = 2; throws an error.
• Good habit: use const by default, and reach for let only when the value truly changes.

Common mistakes

• Use const for values that never change, let for those that do.
• Declare a variable before you use it.

Now you try

• Use let or const to store values.
• Press Check answer to test it.