# JavaScript function to take a number n and generate an array with first n prime numbers

JavascriptWeb DevelopmentObject Oriented Programming

We are required to write a JavaScript function that takes in a number n and returns an array that contains first n prime numbers. We know that prime numbers are those numbers that are only divisible by 1 and themselves like 2, 3, 19, 37, 73 etc.

We will first write a function that checks whether a given number is prime or not and then run a loop to generate n prime numbers. The code to check for prime numbers −

const isPrime = (n) => {
for(let i = 2; i <= n/2; i++){
if(n % i === 0){
return false;
}
};
return true;
};

And the full generating code will be −

## Example

const isPrime = (n) => {
for(let i = 2; i <= n/2; i++){
if(n % i === 0){
return false;
}
};
return true;
};
const generatePrime = num => {
const arr = [];
let i = 2;
while(arr.length < num){
if(isPrime(i)){
arr.push(i);
};
i = i === 2 ? i+1 : i+2;
};
return arr;
};
console.log(generatePrime(6));
console.log(generatePrime(16));
console.log(generatePrime(36));

## Output

The output in the console will be −

[ 2, 3, 5, 7, 11, 13 ]
[
2, 3, 5, 7, 11, 13,
17, 19, 23, 29, 31, 37,
41, 43, 47, 53
]
[
2, 3, 5, 7, 11, 13, 17, 19, 23,
29, 31, 37, 41, 43, 47, 53, 59, 61,
67, 71, 73, 79, 83, 89, 97, 101, 103,
107, 109, 113, 127, 131, 137, 139, 149, 151
]