Day 2: Variables (let & const vs var)

Daily Objective

Learn how to store data in memory using let and const, understand why var is obsolete, and master naming conventions.

1. const vs let vs var

• const (Default choice): For values that will not be reassigned. Prevents accidental bugs.
• let: For variables whose values will change over time (e.g., counters, accumulated totals).
• var (Legacy): Function-scoped, prone to hoisting errors. Never use var in modern code!

const siteName = 'Fran Academy Docs';
let userCount = 42;

userCount = 43; // OK: reassigning let
// siteName = 'New Name'; // TypeError: Assignment to constant variable

2. Naming Rules (camelCase)

• Use camelCase: totalPrice, isUserLoggedIn, shippingAddress.
• Names cannot start with digits and cannot use reserved keywords like class, function, return.

Daily Hands-on Practice (70%)

1. Declare a const for your birth year and a let for your current age.
2. Increment your age variable by 1 using age = age + 1 and log the result.
3. Intentionally try reassigning a const and inspect the error in the console.