JavaScript开发控制台石头剪刀布游戏时布尔变量无法设为true问题

核心问题 #

• JavaScript中布尔值、数字等原始类型是按值传递：当你将game函数内声明的playerWins、computerWins、playerScore、computerScore作为参数传入其他函数时，函数接收的只是这些值的副本，函数内部对参数的修改只会作用于副本，完全不会影响外层的原变量。
  1. playRound函数内部对playerWins、computerWins的赋值，修改的只是函数入参的副本，外层game函数里的两个布尔值永远保持初始的false
  2. 同理checkWinnerInEachRound中对分数的累加操作，也无法修改外层的playerScore、computerScore，最终统计的分数会一直为0

修复方案 #

我们可以调整playRound的逻辑，让它直接返回本轮的胜负结果，不需要通过入参修改外部变量，操作更直观：

1. 修改playRound函数，返回包含胜负状态和提示消息的对象：

// 调整后的playRound函数
function playRound(playerSelection, computerSelection) {
  let playerWins = false;
  let computerWins = false;
  let msg = "";
  if (playerSelection === computerSelection) {
    msg = "No one wins. Move on.";
  } else if (playerSelection === 'Rock' && computerSelection === 'Scissors') {
      playerWins = true;
      msg = "You win! The computer chose Scissors, and Rock beats Scissors.";
  } else if (playerSelection === 'Scissors' && computerSelection === 'Rock') {
      computerWins = true;
      msg = "You lose! The computer chose Rock, and Rock beats Scissors";
  } else if (playerSelection === 'Paper' && computerSelection === 'Rock') {
      playerWins = true;
      msg = "You win! The computer chose Rock, and Paper beats Rock.";
  } else if (playerSelection === 'Rock' && computerSelection === 'Paper') {
      computerWins = true;
      msg = "You lose! The computer chose Paper, and Paper beats Rock.";
  } else if (playerSelection === 'Scissors' && computerSelection === 'Paper') {
      playerWins = true;
      msg = "You win! The computer chose Paper, and Scissors beats Paper.";
  } else if (playerSelection === 'Paper' && computerSelection === 'Scissors') {
      computerWins = true;
      msg = "You lose! The computer chose Scissors, and Scissors beats Paper.";
  }
  return { playerWins, computerWins, msg }
}

2. 调整game函数中调用playRound的逻辑，直接用返回的结果更新状态和分数：

// 原来调用playRound的部分替换为以下代码
const roundResult = playRound(playerSelection, computerSelection);
console.log(roundResult.msg);
console.log(roundResult.playerWins);
console.log(roundResult.computerWins);

// 直接在外层累加分数，无需额外传参
if (roundResult.playerWins) {
  playerScore++;
} else if (roundResult.computerWins) {
  computerScore++;
}

调整完成后，playerWins和computerWins的状态就能正确更新，分数统计逻辑也会正常运行。

内容的提问来源于stack exchange，提问作者Röyal