For each i in the interval {
  check if i has a divisor from 1..i
  if yes => the value is not a prime
  if no => the value is a prime, show it
}

let n = 10;

nextPrime:
for (let i = 2; i <= n; i++) { // for each i...

  for (let j = 2; j < i; j++) { // look for a divisor..
    if (i % j == 0) continue nextPrime; // not a prime, go next i
  }

  alert( i ); // a prime
}