all_unique_chars.js

function allUniqueChars(str) {
  if(!str) return false;

  let checker = 0;
  let flagIndex;
  const length = str.length;

  for (let i = 0; i < length; i++) {
    flagIndex = str[i].charCodeAt(0) - 'a'.charCodeAt(0);
    if ((checker & (1 << flagIndex)) > 0) return false;
    checker |= (1 << flagIndex);
  }

  return true;
}