100 Days of JavaScript🔥– Day 1️⃣:Understanding Data Types & Variables

For Day 1, we're diving straight into what I consider the absolute core concepts of JavaScript: Variables(like a box to hold information)and Data Types (what kind of information is in the box, e.g., text or numbers) .

How We Declare Variables in JavaScript:
In modern JavaScript, we primarily use two keywords to create these containers:

• let: Use let when you expect the value stored in your variable to change (or be reassigned) later in your program.

let firstNumber = 1000; // 'firstNumber ' holds the number 1000
console.log(firstNumber ); // Output: 1000

firstNumber  = 1200;     // We can change its value later!
console.log(firstNumber ); // Output: 1200

• const: Use const when the value of the variable should never change after you've set it. If you try to reassign a const variable, JavaScript will throw an error. This is perfect for values that truly are constant, like a fixed mathematical constant or a username that shouldn't be altered.

//const example

const PIN = 3.14159; // PIN will always be this value
console.log(PIN); // Output: 3.14159

// PIN = 3.0;        // This would cause an error! (Try it in your console!)

• var: You might see var in older code examples. While it still works, let and const were introduced in ES6 (a newer version of JavaScript) to address some confusing behaviors of var. For any new code you write, it's a best practice to stick with let and const.

Naming Our Boxes:

"Just like labeling real-world boxes, there are rules for naming variables: you can use letters, numbers, underscores, and dollar signs, but they must start with a letter, _, or $. Also, JavaScript is case-sensitive, so myName is different from myname."

Code Example:

// Storing text in a variable
const user_Name = "AnsiKadeeja";
console.log(user_Name); // Output: AnsiKadeeja

// Using a boolean
let isLoggedIn = true;
console.log(isLoggedIn); // Output: true

// Showing how 'let' allows changes
let $temperature = 20;
console.log("Current temp:", $temperature); // Output: Current temp: 20
$temperature = 22; // Changing the value
console.log("New temp:", $temperature);   // Output: New temp: 22