for - while.js

FOR LOOP

1.Write a program to print numbers from 1 to 5 using a loop.

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

2.Find the sum of numbers from 1 to 10.

var sum = 0
for (let i =1; i<=10; i++){
     sum+=i
}
console.log(sum)


3. Print even numbers from 1 to 20

for (let i=1; i<=20; i++){
    if (i%2===0){
        console.log(i)
    }
}

4. Reverse a number

let num = 12345
let rev = 0

while (num>0){
    let digit = num % 10
    rev = rev*10+digit;
    num = Math.floor(num/10)
}
console.log(rev)

built-in
let rev= +num.toString().split('').reverse().join('');
console.log(rev).

5. Count digits in a number

let num = 987654

let count = 0

while(num>0){
    count++
    num = Math.floor(num/10)
}
console.log(count)

6. Print elements of an array

let num =[12,34,56,67,90]
for (let i =0; i<=num.length; i++){
    console.log(num[i])
}

7. Find largest number in an array

let num =[4,65,6,7,87,90]
let max = num[0]

for (let i=1; i<num.length; i++){
    if(num[i]>max){
        max =num[i]
    }
}
console.log(max)

8. Pattern printing (important 🔥)

for(let i=1; i<=4;i++){
    let star="";
    for (let j=1; j<=i; j++){
        star+='*'
    }
    console.log(star)
}


9. Break statement
for (let i=1; i<=10; i++){
    if(i===5){
        break
    }
    console.log(i)
}

10. Continue statement

for(let i=1; i<=7; i++){
    if(i===5){
        continue;
    }
    console.log(i)
}

11.Multiplication table

let num =5;

for (let i = 1; i<=20; i++){
    console.log(num + ' x' + i + ' =' + (i*num))
}

12.Factorial of a number

let num = 5
let fact = 1

for (let i =1; i<= num; i++){
    fact*=i
}
console.log(fact)

13.Check whether a number is prime

let num = 8
let count = 0

for(let i=1; i<=num; i++){
    if(num%i === 0){
        count++;
    }
}
if(count === 2){
    console.log("Prime")
}else{
    console.log("Not Prime")
}


14.Check if a number is palindrome

let num = 120
let str = num.toString()
let rev = str.split("").reverse().join("")

if (str === rev) {
  console.log(num + " is a palindrome");
} else {
  console.log(num + " is not a palindrome");
}