JavaScript石头剪刀布游戏函数带参数调用失效问题咨询

问题根源：变量遮蔽（Variable Shadowing） #

你遇到的问题核心是函数参数遮蔽了全局变量：

• 你在全局作用域已经定义了playerSelection和compSelection两个变量，并且通过prompt和立即执行函数给它们赋了值
• 但你给singleround函数声明了同名的参数，这会导致函数内部优先使用参数变量，而不是全局的同名变量
• 现在你的singleround是立即执行函数（IIFE），你没有给它传递任何参数，所以函数内部的playerSelection和compSelection都是undefined——两个undefined相等，自然触发平局提示
• 当你去掉函数的参数时，函数内部会自动向上查找全局作用域的同名变量，所以逻辑恢复正常

两种修正方案 #

方案1：去掉函数参数，直接使用全局变量

适合简单的单轮游戏场景，直接移除函数的参数声明，让函数使用全局的变量：

(function singleround() {
  // 原函数内的判断逻辑完全不变
  if (playerSelection === "rock" && compSelection === "paper") {
    console.log("Oh No! You lost, Paper beats Rock :(");
  } else if (playerSelection === "rock" && compSelection === "scissors") {
    console.log("Well done! You won, Rock beats Scissors!");
  } else if (playerSelection === "paper" && compSelection === "rock") {
    console.log("Well done! You won, Paper beats Rock!");
  } else if (playerSelection === "paper" && compSelection === "scissors") {
    console.log("Oh No! You lost, Scissors beats Paper :(");
  } else if (playerSelection === "scissors" && compSelection === "rock") {
    console.log("Oh No! You lost, Rock beats Scissors :(");
  } else if (playerSelection === "scissors" && compSelection === "paper") {
    console.log("Well done! You won, Scissors beats Paper!");
  } else if (playerSelection === compSelection) {
    console.log("It's a tie! Try again.");
  } else {
    console.log("Uh Oh! Something's gone wrong. Refresh the page to try again!");
  }
})();

方案2：保留参数，改为普通函数并主动传参

如果后续要扩展多轮游戏，推荐这种方式，让函数更独立：

// 把立即执行函数改成普通函数
function singleround(playerSelection, compSelection) {
  // 原判断逻辑不变
  if (playerSelection === "rock" && compSelection === "paper") {
    console.log("Oh No! You lost, Paper beats Rock :(");
  } else if (playerSelection === "rock" && compSelection === "scissors") {
    console.log("Well done! You won, Rock beats Scissors!");
  } else if (playerSelection === "paper" && compSelection === "rock") {
    console.log("Well done! You won, Paper beats Rock!");
  } else if (playerSelection === "paper" && compSelection === "scissors") {
    console.log("Oh No! You lost, Scissors beats Paper :(");
  } else if (playerSelection === "scissors" && compSelection === "rock") {
    console.log("Oh No! You lost, Rock beats Scissors :(");
  } else if (playerSelection === "scissors" && compSelection === "paper") {
    console.log("Well done! You won, Scissors beats Paper!");
  } else if (playerSelection === compSelection) {
    console.log("It's a tie! Try again.");
  } else {
    console.log("Uh Oh! Something's gone wrong. Refresh the page to try again!");
  }
}

// 调用函数时传入全局变量
singleround(playerSelection, compSelection);

额外优化建议 #

你的getComputerChoice立即执行函数可以改成更清晰的普通函数，避免全局变量randomNumber的冗余：

function getComputerChoice() {
  const randomNumber = Math.floor(Math.random() * 3) + 1;
  if (randomNumber === 1) {
    return "rock";
  } else if (randomNumber === 2) {
    return "paper";
  }
  return "scissors";
}

// 直接赋值给compSelection
const compSelection = getComputerChoice();

内容的提问来源于stack exchange，提问作者Guépardeau