如何从一组字符中选择唯一的字符串

function selectUniqueString(characters) {
  const uniqueChars = new Set();
  
  for (let i = 0; i < characters.length; i++) {
    uniqueChars.add(characters[i]);
  }
  
  let uniqueString = "";
  
  uniqueChars.forEach((char) => {
    uniqueString += char;
  });
  
  return uniqueString;
}

const characters = "abracadabra";
const uniqueString = selectUniqueString(characters);
console.log(uniqueString);  // 输出: "abrcd"

exports.main_handler = async (event, context, callback) => {
  const characters = event.characters;
  const uniqueChars = new Set();
  
  for (let i = 0; i < characters.length; i++) {
    uniqueChars.add(characters[i]);
  }
  
  let uniqueString = "";
  
  uniqueChars.forEach((char) => {
    uniqueString += char;
  });
  
  return uniqueString;
};