我在哪里失去随机性？

Question

所以我正在构建一个石头、纸、剪刀游戏。我想让 math.random() 给我一个随机结果，我将其与用户选择的结果进行比较。

它主要是有效的。我什至认为它在一段时间内完全有效，但我在某些时候失去了随机性。

为了尝试它，我输入了一个固定的“用户”选项，并使用 setInterval(myfunction, 20) 运行代码几百次。他们总是不平衡的胜利，而且总是有相同的结果：

如果我用 playerPick = 1 运行它，计算机总是获胜。

如果我使用 playerPick = 2 或 3 运行它，用户总是获胜。

任何人都可以看到我犯错的地方吗？

//Global variable and constants.

const ROCK = 1;
const PAPER = 2;
const SCISSORS = 3;

//This is the game.

function whoWins(){
    const playerPick = 2; //for debugging, it can be 1, 2, or 3.
    const computer = computerPick();
    if (playerPick == computer){
        return draw();
    } else if (playerPick == 1 && computer == 2){
        return lose();
    } else if (playerPick == 2 && computer == 3){
        return lose();
    } else if (playerPick == 3 && computer == 1){
        return lose();
    } else {
        return win();
    }
}

//These are the inputs for the game.

rockButton.addEventListener('click', () => {
    playerPick = ROCK;
    return whoWins()});
paperButton.addEventListener('click', () => {
    playerPick = PAPER;
    return whoWins()});
scissorsButton.addEventListener('click', () => {
    playerPick = SCISSORS;
    return whoWins()});

function computerPick() {
    let computerChoice = '';
    const getRandom = Math.random;
    if (getRandom() >= 2/3) {
        computerChoice = ROCK;
    } else if (getRandom() >= 1/3){
        computerChoice = PAPER;
    } else {
        computerChoice = SCISSORS;
    }
    return computerChoice;
}

我对这一切都很陌生，但仍然不是随机的。

Answer 1

这应该是一个简单的修复，如 cmets 中所述，您需要调用一次 Math.random，否则概率会出现偏差。

我认为使用原始代码的 PAPER 的概率应该是 0.66 * 0.66 = ~ 44%，而 SCISSORS 的概率应该是 0.66 * 0.33 = ~ 22%。新功能应该可以解决这个问题。

const ROCK = 1;
const PAPER = 2;
const SCISSORS = 3;

// Original computerPick function
function computerPickOriginal() {
    let computerChoice = '';
    const getRandom = Math.random;
    if (getRandom() >= 2/3) {
        computerChoice = ROCK;
    } else if (getRandom() >= 1/3){
        computerChoice = PAPER;
    } else {
        computerChoice = SCISSORS;
    }
    return computerChoice;
}

// Fixed computerPick function.
function computerPick() {
    let computerChoice = '';
    const choice = Math.random();
    if (choice >= 2/3) {
        computerChoice = ROCK;
    } else if (choice >= 1/3){
        computerChoice = PAPER;
    } else {
        computerChoice = SCISSORS;
    }
    return computerChoice;
}

function decodeChoice(choice) {
    if (choice == ROCK) return "Rock";
    if (choice == PAPER) return "Paper";
    if (choice == SCISSORS) return "Scissors";
}

// Check the distribution of each version of the code.
console.log("Checking distributions (10000 picks)..");
let original_counts = {};
let counts = {};
for(let i = 0; i < 10000; i++) {
  let k = computerPick();
  counts[k] = (counts[k] || 0) + 1;
  let k2 = computerPickOriginal();
  original_counts[k2] = (original_counts[k2] || 0) + 1;
}

console.log('Computer Pick Distribution (original): ', Object.entries(original_counts).map(([key,value]) => `${decodeChoice(key)}: ${value}`));
console.log('Computer Pick Distribution (fixed): ', Object.entries(counts).map(([key,value]) => `${decodeChoice(key)}: ${value}`));

Answer 2

为了将来参考，您可能会发现使用数组更容易。

const getRandomChoice = () => {
  const options = ['Rock', 'Paper', 'Scissors'];

  const randomIndex = Math.floor(Math.random() * options.length);

  const choice = options[randomIndex];
  return choice;
}

const counts = {};

for(let i = 0; i < 10000; i++) {
  let p = getRandomChoice();
  counts[p] = (counts[p] || 0) + 1;
}

console.log(counts);

通过将Math.random 的结果乘以数组 (3) 的长度，我们可以得到一个介于 [0, 3) 之间的值（不包括 3）。然后我们调用Math.floor 来“删除”任何小数。