javascript-array

// Declare an array without a size
const arr = [];

// Declrate an array with a size
const arr2 = new Array(8);

console.log({"typeOfArr": typeof arr});
console.log({"typeOfArr2": typeof arr2});

// Populate array arr
arr.push(1);
arr.push(2);
arr.push(3, 4);
arr.push(5);
arr.push(6, 7, 8);

// Populate array arr2
arr2.push(1);
arr2.push(2);
arr2.push(3, 4);
arr2.push(5);
arr2.push(6, 7, 8);
arr2.push(9);

console.log({first: arr[0]});
console.log({second: arr[1]});
console.log({third: arr[2]});
console.log({fourth: arr[3]});
console.log({fifth: arr[4]});
console.log({sixth: arr[5]});
console.log({seventh: arr[6]});
console.log({eighth: arr[7]});

for (let index = 0; index < arr.length; index++) {
	console.log({index: index, value: arr[index]});
}

arr.forEach((value, index) => {
	console.log({index: index, value: arr[index]});
});

for (const value of arr) {
    console.log({value: value});
}

// while loop
let index = 0;
while (index < arr.length) {
	console.log({index: index, value: arr[index]});
    index++;
}

// do while loop
index = 0;
do {
	console.log({index: index, value: arr[index]});
    index++;
} while (index < arr.length)

javascript-factorial

const factorial = (n) => {
  if (n > 1) {
    return n * factorial(n - 1);
  }
  
  return n;
}

const result = factorial(4);
console.log({result});

javascript-stack

class Stack {
  constructor() {
    this.data = [];
  }
  
  push(n) {
    this.data.unshift(n);
  }
  
  top() {
    return this.data[0];
  }
  
  pop() {
    return this.data.shift();
  }
  
  toString() {
    return this.data;
  }
}

const stack = new Stack();
stack.push(10);
stack.push(20);
stack.push(30);
stack.push(40);
console.log(stack.toString());
console.log(stack.top());
console.log(stack.pop());
console.log(stack.toString());