JavaScript剪刀石头布游戏：优化prompt输入处理与完善胜负判断逻辑

let playgame = confirm("Do you want to play game?");
if (playgame) {
  let startgame = prompt("Choose from r, p, s?");

  // 检查用户是否点击了“取消”
  if (startgame !== null) { // 用户没有点击“取消”
    let playerchoice = startgame.trim().toLowerCase(); // 清除空格并转小写

    // 检查玩家输入是否有效
    if (playerchoice === "r" || playerchoice === "s" || playerchoice === "p") {
      // 游戏核心逻辑
      // ... (此处省略，将在问题二中详细说明)

    } else {
      // 用户输入无效（包括空字符串）
      alert("你没有选择 r, p, s");
    }
  } else {
    // 用户点击了“取消”
    alert("改变主意了？没关系");
  }
} else {
  alert("下次再玩吧！");
}

// ... (接问题一的输入处理代码)

    if (playerchoice === "r" || playerchoice === "s" || playerchoice === "p") {
      // 电脑随机选择
      let compchoiceNum = Math.floor(Math.random() * 3); // 0, 1, 2
      let computer;
      if (compchoiceNum === 0) {
        computer = "r";
      } else if (compchoiceNum === 1) {
        computer = "p"; // 修正：原来是s，应该对应p
      } else { // compchoiceNum === 2
        computer = "s"; // 修正：原来是p，应该对应s
      }

      // 提示电脑的选择
      alert(`玩家选择了: ${playerchoice.toUpperCase()}\n电脑选择了: ${computer.toUpperCase()}`);

      // 判断胜负
      if (playerchoice === computer) {
        alert("平局！");
      } else if (
        (playerchoice === "r" && computer === "s") || // 石头胜剪刀
        (playerchoice === "p" && computer === "r") || // 布胜石头
        (playerchoice === "s" && computer === "p")    // 剪刀胜布
      ) {
        alert("玩家获胜！");
      } else {
        // 其他所有情况都是电脑获胜
        alert("电脑获胜！");
      }
    } else {
      alert("你没有选择 r, p, s");
    }
// ... (接问题一的输入处理代码)

let playgame = confirm("你想玩游戏吗？");

if (playgame) {
  let isValidInput = false;
  let playerchoice;

  // 使用循环确保玩家输入有效
  while (!isValidInput) {
    let startgame = prompt("请选择：r (石头), p (布), s (剪刀)");

    if (startgame === null) { // 用户点击了“取消”
      alert("改变主意了？没关系，下次再玩。");
      playgame = false; // 退出游戏
      break; // 退出循环
    }

    playerchoice = startgame.trim().toLowerCase();

    if (playerchoice === "r" || playerchoice === "s" || playerchoice === "p") {
      isValidInput = true; // 输入有效，退出循环
    } else {
      alert("无效输入。请选择 r, p, 或 s。");
    }
  }

  if (playgame) { // 只有当用户没有取消游戏时才继续
    // 电脑随机选择
    const compchoiceNum = Math.floor(Math.random() * 3); // 0, 1, 2
    let computer;
    if (compchoiceNum === 0) {
      computer = "r";
    } else if (compchoiceNum === 1) {
      computer = "p";
    } else {
      computer = "s";
    }

    // 提示玩家和电脑的选择
    alert(`你选择了: ${playerchoice.toUpperCase()}\n电脑选择了: ${computer.toUpperCase()}`);

    // 判断胜负
    if (playerchoice === computer) {
      alert("平局！");
    } else if (
      (playerchoice === "r" && computer === "s") || // 石头胜剪刀
      (playerchoice === "p" && computer === "r") || // 布胜石头
      (playerchoice === "s" && computer === "p")    // 剪刀胜布
    ) {
      alert("恭喜你，玩家获胜！");
    } else {
      alert("很遗憾，电脑获胜！");
    }
  }

} else {
  alert("下次再玩吧！");
}