summing primes from 2 million

primesum.js

console.log(primesum(2000000))

function primesum(m){

  let ret = 7, i = 1 //(ret=7) prepopulate 2 and 5, dropped by optimization
  while (i++ < m) {
    if (isprime(i))
      ret += i
  }
  return ret

  function isprime(n){
    let l = n
    let preflight = Number(String(n).slice(-1))
    if ( preflight === 5 || !(preflight%2) )
      return false
    while(l-- > 2)
      if (!(n % l))
        return false
    return true
  }
}