Day-6- Loops in JS

 //Iterate 0 to 10 using for loop, do the same using while and do while loop
  for(let i = 0; i<countries.length; i++){
    console.log(i,countries[i])
  }
  //using while loop
  let i = 0
  while(i<=countries.length){
    console.log("In while loop",i,countries[i])
    i++;
  }
  //using do while loop
  let j =0;
  do{
    console.log("In do while loop",j+1,countries[j])
    j++;

  }while(j<countries.length)

//Iterate 10 to 0 using for loop, do the same using while and do while loop
  for(let i = 10; i>=0; i--){
    console.log(i)
  }
//using do while loop
  let i = 10;
  do{
    console.log("using do while",i)
    i--;
  }while(i>=0)
//using while loop
let j = 10;
while(j>=0){
  console.log("using while loop",j)
  j--;
}
//iterate 0 to  n using for loop
var n = parseInt(prompt("Enter the value of n"));
if(!isNaN(n)&&typeof n === 'number'){
for(let i = 0; i<n;i++){
    console.log(i)
}
}else{
console.log("Please Enter a nummber")
}
  //iterate 0 to  n using for loop
var n = prompt("Enter the value of n")
for(let i = 0; i<n;i++){
    console.log(i)
}

Write a loop that makes the following pattern using console.log():

    #
    ##
    ###
    ####
    #####
    ######
    #######

Solution:

for(let i = 1; i<8;i++){
  console.log("#".repeat(i));
}
//using traditional method
for(let i = 1; i<8;i++){
    let count = ''
    for(let j = 1;j<=i;j++){
      count+="#"
      console.log("i am in j loop")
    }
    console.log(count);
  }

Use loop to print the following pattern:

0 x 0 = 0
1 x 1 = 1
2 x 2 = 4
3 x 3 = 9
4 x 4 = 16
5 x 5 = 25
6 x 6 = 36
7 x 7 = 49
8 x 8 = 64
9 x 9 = 81
10 x 10 = 100

Solution

for(let i = 0; i<=10; i++){
    console.log(i+" x "+i+" = "+i*i)
  }

Using loop print the following pattern

 i    i^2   i^3
 0    0     0
 1    1     1
 2    4     8
 3    9     27
 4    16    64
 5    25    125
 6    36    216
 7    49    343
 8    64    512
 9    81    729
 10   100   1000

for(let i = 0; i<=10;i++){
    console.log(i ,Math.pow(i,2),Math.pow(i,3))
  }

Use for loop to iterate from 0 to 100 and print only even numbers

   for(let i = 0;i<=100;i++){
      if(i%2===0){
        console.log(i)
      }
   }

Use for loop to iterate from 0 to 100 and print only odd numbers

  for(let i = 0;i<=100;i++){
      if(i%2!==0){
        console.log(i)
      }
   }

Use for loop to iterate from 0 to 100 and print only prime numbers
Prime numbers have only 2 factors, one themselves and other is one. We have to find it using JavaScript. so first off, we know that 0 and 1 are not prime numbers.

The loop will check if the number divides with no remainder left, we check until the square of the number.


  const isPrime = (num)=>{
    if(num<=1) return false;
    for(let i = 2; i<Math.sqrt(num); i++){
        if(num%2===0) return false
    }
    return true;
    }
    for(let i = 0; i<=100; i++){
        if(isPrime(i)){
              console.log(i)
        }
      }

Use for loop to iterate from 0 to 100 and print the sum of all numbers.

  let sum = 0;
  for(let i =0; i<=100; i++){
    sum+=i;
  }
  console.log(sum)

Use for loop to iterate from 0 to 100 and print the sum of all evens and the sum of all odds.

 //output
 The sum of all evens from 0 to 100 is 2550. And the sum of all odds from 0 to 100 is 2500.
 //solution
 let sum = 0;
 let Oddsum = 0;
 for(let i =0; i<=100; i++){
   if(i%2===0)  sum+=i;
     else Oddsum+=i;
 }
 console.log("The sum of all evens from 0 to 100 is", sum + ".And the sum of all odds from 0 to 100 is "+ Oddsum )

Now, Print sum of evens and sum of odds as array.

  let arrayNum = [];
  let sum = 0;
  let Oddsum = 0;
  for(let i =0; i<=100; i++){
    if(i%2===0)  sum+=i;
      else Oddsum+=i;
  }
  arrayNum.push(sum);
  arrayNum.push(Oddsum)
  console.log(arrayNum)

Develop a small script which generate array of 5 random numbers
We can get random numbers in Javascript using Math.random

  //Develop a small script which generate array of 5 random numbers
  let random5Numbers = [];
  for(let i = 0; i<5; i++){
    random5Numbers.push(Math.floor(Math.random()*100))
  }
  console.log(random5Numbers);

Develop a small script which generate array of 5 random numbers and the numbers must be unique

 let random5UniqueNumbers = [];
 for(let i = 0; i<5; i++){
     let randomNumber = Math.floor(Math.random()*100)
     if(random5UniqueNumbers.indexOf(randomNumber)===-1)
     random5UniqueNumbers.push(randomNumber)
 }
 console.log(random5UniqueNumbers)

Develop a small script which generate a six characters random id:

const characters ='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
const generateID =() => {
  let ID = '';
  const charactersLength = characters.length;
  for(let i = 0; i<6; i++){
    ID += characters.charAt(Math.floor(Math.random()*charactersLength))
  }
  return ID;
}
console.log(generateID())

Exercise-2

Develop a small script which generate any number of characters random id:

 const generateID = (length)=>{
  const characters = 'abcdefghijklmnopqrstuvwxyz1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ'
  let ID = '';
  const charactersLength = characters.length;
  for(let i = 0; i<length; i++){
    ID += characters.charAt(Math.floor(Math.random()*charactersLength))
  }
  return ID;
 }

 length = Math.floor(Math.random()*20)

 console.log(generateID(length))

Write a script which generates a random hexadecimal number.

const generateHexId = () =>{
  const hexID = '0123456789ABCDEF';
  let randomHex = '';
  for(let i = 0; i<6;i++){
    randomHex += hexID.charAt(Math.floor(Math.random()*(hexID.length)))
  }
  return randomHex;
}
console.log(generateHexId())

Write a script which generates a random rgb color number.

const randomRGB = () => {
  const red = Math.floor(Math.random()*256);
  const  green = Math.floor(Math.random()*256);
  const blue = Math.floor(Math.random()*256);
  return `rgb(${red},${green},${blue})`
}

console.log(randomRGB())

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Day-6- Loops in JS

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