Prime Number Questions in JavaScript

Hello Everyone! This blog will cover Prime Numbers during The Hacking School Coding Bootcamp, Remote.

What is Prime Number?

A prime number is a natural number greater than 1, which is only divisible by 1 and itself. First few prime numbers are : 2 3 5 7 11 13 17 19 23 …..

1. Write a javascript program to check the given number is a prime number or not.

function prime(n){
var factorsCount=0;
 for(var i=1; i<=n;i++){
   if(n%i ===0 ){
      factorsCount++;
   }
 }
 if(factorsCount === 2){
     console.log(`The Given number ${n} is a prime number`);
 }else{ 
     console.log("Not prime");
 }
}
prime(3);

Output: The Given number 3 is a prime number.

2. Write a javascript program to print the count of prime numbers in the given data array.

var data=[-22,33,11,44,13,78,100,23];
var prime=0;
for(var index=0;index<data.length;index++){
   var count=0;
   for(var i=1;i<=data[index];i++){
     if(data[index]%i===0 ){
       count++;
     }
   }
   if(count === 2){
     prime++;
   }
}
console.log("Count theprime number:",prime);

Output: Count the prime number: 3.

3. Using a try-catch method to write a javascript program to print the count of prime numbers in the given data array.

try{
var data=[10,15,27,19,2,3,5,7];
var primeCounter=0;
for(index=0;index<data.length;index++){
   var factors=0;
   for(var j=1;j<=data[index];j++){
     if(data[index]%j===0){
       factors++;
     }
   }
   if(factors===2){
     primeCounter++;
   }
}
console.log(“Count the prime number”,primeCounter);
}
catch(err){ 
   console.log(“something wrong” + err.message);
}

Output: Count the prime number: 5.

4. Print the prime number from range (m,n), where,m,n is a positive number, and count the prime number.

function prime(m,num){
 var prime=" ";
 var count=0;
 for(var k=m;k<=num;k++){ 
   var store = 0;
   for (var j = 2; j<=k; j++){
     if(k% j === 0){
        store++;
     }
   }
   if(store === 1){
    prime=prime+k +" ";
    count=count+1;  //count the number
   }
 }
 console.log("Prime Number:",prime);
 console.log("Count the prime number:",count);
}
prime(10,20);

Output: Prime Number:11 13 17 19. Count the prime number: 4.