shuffle.js

const shuffle = list => {
  const shuffledList = [...list];

  for (
    let currentIndex = shuffledList.length - 1;
    currentIndex > 0;
    currentIndex--
  ) {
    const nextIndex = Math.floor(Math.random() * (currentIndex + 1));
    const nextItem = shuffledList[nextIndex];
    const currentItem = shuffledList[currentIndex];

    shuffledList[nextIndex] = currentItem;
    shuffledList[currentIndex] = nextItem;
  }

  return shuffledList;
};

const shuffle11 = list => {
  const shuffledList = [...list];

  shuffledList.forEach((item, index) => {
    const nextIndex = Math.floor(Math.random() * (list.length - index) + index);
    const nextItem = shuffledList[nextIndex];

    shuffledList[nextIndex] = item;
    shuffledList[index] = nextItem;
  });

  return shuffledList;
};

const shuffle2 = list => {
  const shuffledList = [...list];

  shuffledList.forEach((item, index) => {
    const nextIndex = Math.round(Math.random() * (list.length - 1));
    const nextItem = shuffledList[nextIndex];

    shuffledList[nextIndex] = item;
    shuffledList[index] = nextItem;
  });

  return shuffledList;
};

const shuffle3 = list => {
  const shuffledList = [...list];

  for (let i = shuffledList.length - 1; i > 0; i--) {
    const index = Math.round(Math.random() * i);
    const item = shuffledList[index];

    shuffledList.splice(index, 1);
    shuffledList.push(item);
  }

  return shuffledList;
};

const progress = value => {
  return new Array(Math.floor(value)).fill('=').join('');
};

const execute = shuffleFunc => {
  const times = 1000 * 1000 * 10;
  const result = {};

  for (let i = 0; i < times; i++) {
    const sl = shuffleFunc([1, 2, 3, 4]);
    const k = sl.join('');

    if (result[k] == null) {
      result[k] = 1;
    } else {
      result[k] += 1;
    }
  }

  Object.keys(result).forEach((key, index) => {
    const ratio = (result[key] * 100) / times;

    console.log(
      `#${index + 1} ${key} ${result[key]} ${progress(ratio)} ${ratio}`
    );
  });

  console.log(Object.values(result).reduce((prev, curr) => prev + curr, 0));
};

console.log('shuffle#1');
execute(shuffle);
// execute(shuffle);
// execute(shuffle);
console.log('---------------');
console.log('shuffle#11');
execute(shuffle11);
// console.log('---------------');
// console.log('shuffle#2');
// execute(shuffle2);
// execute(shuffle2);
// execute(shuffle2);
// console.log('---------------');
// console.log('shuffle#3');
// execute(shuffle3);
// execute(shuffle3);
// execute(shuffle3);