js_code_golf_1_2.js

const prime2 = end => {
  if(end < 2) return [];
  
  const prime = [2], num = [];
  let curr = 2, i = 3, j;
  while(i <= end){
    num.push(i);
    i += 2;
  }
  while(num.length){
    prime.push(curr = num.shift());
    i = num.length;
    j = curr * curr;
    while(i--){
      if(num[i] < j) break;
      if(num[i] % curr == 0) num.splice(i, 1);
    }
    if(j > num[num.length - 1]) break;
  }
  return prime.concat(num);
}