find_all_prime_numbers_in_an_array.md

Find All Prime Numbers in an Array

Find All Prime Numbers in an Array

To find all prime numbers in an array, check each number in the array to see if it is prime.

Algorithm:

1. Define a helper function isPrime to check if a number is prime.
2. Iterate through the array, calling isPrime on each element.
3. Collect the prime numbers and return them.

Example:

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

function findPrimes(arr) {
    return arr.filter(isPrime);
}

// Example usage
console.log(findPrimes([1, 2, 3, 4, 5, 6])); // Output: [2, 3, 5]
console.log(findPrimes([10, 15, 23, 30])); // Output: [23]

This method has a time complexity of O(n * sqrt(m)), where n is the length of the array and m is the largest number in the array.

Tags: intermediate, JavaScript, Arrays, Algorithm