js_code_golf_1_4.js

const prime4 = end =>{
  if(end < 2) return [];
  
  const num = [2];
  for(let i = 3; i <= end; i += 2) num.push(i);
  for(let i = 1, j = num.length, curr; i < j; i++){
    if(curr = num[i]){
      const min = curr * curr;
      if(end < min) break;
      for(let k = (min - 1) / 2; k < j; k += curr) {
        if(num[k] != 0 && num[k] % curr == 0) num[k] = 0;
      }
    }
  }
  return num.filter(v => v);
}