create isPrime()

Question

A Prime number is a natural number greater than 1 that is divisible only by itself and 1, such as 2,3,5....

You are asked to implement isPrime() to check if a number is prime.

Follow-up

What is the time cost of your implementation ? can you improve your approach to have the fewest comparisons?

Code

/**
 * @param {number} num - positive integer
 */
function isPrime(num) {
  // your code here
}

Source

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