JS isPrime

isPrime.js

/**
 * by definition, primes cannot be negative
 */
const isPrime = value => {
    for(var i = 2; i < value; i++) {
        if(value % i === 0) {
            return false;
        }
    }
    return value > 1;
}

var isPrime = n => n > 1 && Array.from({ length: Math.floor(Math.sqrt(n)) - 1 },(_,i) => i + 2).every(m => n % m);
// or
var isPrime = n => n>1 && !/^(oo+)\1+$/.test('o'.repeat(n)) // inefficient for big numbers

// test - generate list of all primes 1 - 101
Array.from({length:101}, (_,i)=>i).filter(isPrime)