When it comes to programming in Javascript, understanding variables and data types is essential. These fundamental concepts form the building blocks of any software application.

Variables

In NodeJS, variables act as “containers” for storing data values. They provide a means to reference and manipulate information throughout your code. To declare a variable, you can use the var, let, or const keywords.

• var: Used for declaring variables in older versions of JavaScript, but often avoided due to scope-related issues(⏭️).
• let: Introduced to address the scoping problems of var, let defines variables with block-level scope, making them a better choice for most situations.
• const: Similar to let, but once assigned a value, a const variable cannot be reassigned. It is ideal for values that shouldn’t change during the program’s execution.

Declaration

Declaration is the process of introducing a variable to your program. It involves specifying the variable’s name. In JavaScript and NodeJS, variables can be declared using the var, let, or const keywords. We want to use let or const and not var.

Variables in JS are case sensitive

console.log is used for printing value in the console. As to why it has a dot(.) and parenthesis(()) we will cover it later(⏭️).

let playerName;
console.log(playerName); // undefined

Above, we declared a variable playerName but it is empty or undefined when we talk about JS.

Initialization

Initialization refers to the act of assigning an initial value to a variable when it’s declared. Proper initialization ensures that variables start with a meaningful value, minimizing unexpected behaviors and bugs in your code.

let counter = 0; // Initializing 'counter' with the value 0
let playerName = "Alice"; // Declaring and initializing 'playerName'
const maxScore = 100; // Declaring and initializing 'maxScore'

const MaxScore = 50;
// maxScore and MaxScore are two different variables (case sensitive)
console.log(playerName); // Alice
console.log(playerName, maxScore); // Alice 100
console.log(playerName, maxScore, MaxScore); // Alice 100 50

Data Types

NodeJS supports several data types, each serving a distinct purpose:

1. Primitive Data Types: These include numbers, strings, booleans, null, and undefined.

2. Complex Data Types: These are objects and functions.

3. Special Data Types: These consist of Symbol and BigInt, introduced in later versions of JavaScript.

Let’s go through each of those:

Primitive Data Types

1. Numbers

Numbers in NodeJS can be integers or floating-point numbers.

let age = 25; // Integer
let temperature = 98.6; // Floating-point

2. Strings

Strings represent textual data and are enclosed in single or double quotes or backticks.

let name = "Alice";
let message = "Hello, NodeJS!";
let motivation = `This is fun`;

3. Booleans

Booleans represent two values: true or false, often used for conditional statements.

let isRaining = true;
let isLoggedIn = false;

4. null and undefined

Both null and undefined represent the absence of a value, but they are used in different contexts. undefined means that a variable exists, but it doesn’t have any value associated with it yet. null represents the absence of a value in situations where the absence is intentional and has semantic meaning.

let emptyValue = null;
let notDefined = undefined;

Complex Data Types

1. Objects

Objects are collections of key-value pairs, allowing you to group related data together.

let person = { name: "Bob", age: 30 };

2. Arrays

Arrays store multiple values in a list.

let colors = ["red", "green", "blue"];
let numbers = [1, 2, 3, 4];
let mixed = ["a", 1, "f", 45];

Special Data Types

We’ll look into these more closely in intermediate tutorials

1. Symbol

Symbols are unique and often used as object property identifiers.

const idSymbol = Symbol("id");

2. BigInt

BigInt is used to represent large integers beyond the limits of the Number data type. It ends with an n. The Number.MAX_SAFE_INTEGER static data property represents the maximum safe integer in JavaScript and it is (25³ – 1).

const bigNumber = 1234567890123456789012345678901234567890n;

What now?

Now think of some everyday usecases and create variables from those. If nothing comes to mind here are a few to start with: shopping cart, product in the store, and even you.