# DAY 2 JAVASCRIPT CORE CONCEPTS CHEATSHEET

Introduction Welcome to Day 2 of your JavaScript learning journey! Today, we’ll dive deep into the Core Concepts of JavaScript that every beginner must know before building real-world projects. Mastering these basics will make your coding life easier and help you understand advanced topics faster. 1. VARIABLES IN JAVASCRIPT Variables are containers used to store data values. Declaring Variables: var name = "Dhanian"; // Old way let age = 25; // Modern & Recommended const country = "Kenya"; // Cannot be changed Keyword Usage Can Reassign var Avoid using Yes let Recommended Yes const Recommended No (constant) 2. DATA TYPES IN JAVASCRIPT JavaScript has 8 basic data types: String → Text → "Hello" Number → 123, 45.6 Boolean → true or false Undefined → Value not assigned Null → Empty or unknown Object → Complex data Symbol → Unique identifiers BigInt → Large integers Example: let name = "Dhanian"; // String let age = 25; // Number let isOnline = true; // Boolean let city; // Undefined let car = null; // Null 3. OPERATORS IN JAVASCRIPT Type Example Meaning Arithmetic + - * / % Math operations Assignment = += -= Assign values Comparison == === != Compare values Logical && Example: let a = 10; let b = 5; console.log(a + b); // 15 console.log(a > b); // true console.log(a == 10); // true 4. CONDITIONAL STATEMENTS Make decisions in your code. if / else if / else let age = 18; if (age >= 18) { console.log("You are an adult."); } else { console.log("You are a minor."); } 5. SWITCH STATEMENT let day = "Monday"; switch(day) { case "Monday": console.log("Start of the week"); break; case "Friday": console.log("Weekend loading..."); break; default: console.log("Just another day"); } 6. LOOPS IN JAVASCRIPT Loops help us repeat tasks. for loop for(let i = 1; i

var name = "Dhanian";  // Old way
let age = 25;          // Modern & Recommended
const country = "Kenya"; // Cannot be changed

let name = "Dhanian";  // String
let age = 25;          // Number
let isOnline = true;   // Boolean
let city;              // Undefined
let car = null;        // Null

let a = 10;
let b = 5;

console.log(a + b);   // 15
console.log(a > b);   // true
console.log(a == 10); // true

let age = 18;

if (age >= 18) {
  console.log("You are an adult.");
} else {
  console.log("You are a minor.");
}

let day = "Monday";

switch(day) {
  case "Monday":
    console.log("Start of the week");
    break;
  case "Friday":
    console.log("Weekend loading...");
    break;
  default:
    console.log("Just another day");
}

for(let i = 1; i <= 5; i++) {
  console.log(i);
}

let i = 1;
while(i <= 5) {
  console.log(i);
  i++;
}

function greet() {
  console.log("Hello World");
}

greet();

function add(a, b) {
  return a + b;
}

console.log(add(5, 3));  // 8

let fruits = ["Mango", "Banana", "Apple"];

console.log(fruits[0]);  // Mango

fruits.push("Orange");   // Add item
fruits.pop();            // Remove last item
console.log(fruits.length); // Count items

let person = {
  name: "Dhanian",
  age: 25,
  country: "Kenya"
};

console.log(person.name);  // Dhanian

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