gistfile1.txt

// ** check for validate parenthesis

const isValidParenthesis = str => {
  let brackets = 0;
  for (let i = 0; i < str.length; i++) {
    if (str.charAt(i) === "(") {
      brackets++;
    } else if (str.charAt(i) === ")") {
      brackets--;
    } else {
      return false;
    }
  }
  return brackets === 0;
};

// ** flatten array

const flatten = (arr, result = []) => {
  arr.forEach(element => {
    if (Array.isArray(element)) {
      flatten(element, result);
    } else {
      result.push(element);
    }
  });
  return result;
};

// ** random ids

const generateRandomId = () => {
  const getRandomElementFromArray = arr => {
    return arr[Math.floor(Math.random() * arr.length)];
  };
  const characters = [
    "a",
    "b",
    "c",
    "d",
    "e",
    "f",
    "g",
    "h",
    "i",
    "j",
    "k",
    "l",
    "m",
    "n",
    "o",
    "p",
    "q",
    "r",
    "s",
    "t",
    "u",
    "v",
    "w",
    "x",
    "y",
    "0",
    "1",
    "2",
    "3",
    "4",
    "5",
    "6",
    "7",
    "8",
    "9"
  ];
  const part1 = `${getRandomElementFromArray(
    characters
  )}${getRandomElementFromArray(characters)}${getRandomElementFromArray(
    characters
  )}`;
  const part2 = `${getRandomElementFromArray(
    characters
  )}${getRandomElementFromArray(characters)}${getRandomElementFromArray(
    characters
  )}`;
  const part3 = `${getRandomElementFromArray(
    characters
  )}${getRandomElementFromArray(characters)}${getRandomElementFromArray(
    characters
  )}`;
  return `${part1}-${part2}-${part3}`;
};

const arrayUnique = arr => {
  return arr.filter((item, index) => {
    return arr.indexOf(item) >= index;
  });
};

// generate 1000 random ids
let ids = [];
for (let i = 0; i < 1000; i++) {
  ids.push(generateRandomId());
}

// ids.length === 1000
// find unique ids in 'ids' array but removing all duplicates, arrayUnique(ids).length
// find percentage of duplicates

console.log((ids.length / arrayUnique(ids).length) * 100);