JavaScript石头剪刀布循环时电脑随机选择值不更新问题求解

错误根源 #

随机选择逻辑写在了computerPlay()函数的外部，脚本初始化阶段仅会执行1次随机计算，把结果存在全局变量randomValue中。后续5轮循环每次调用computerPlay()都只是返回这个第一次生成的固定值，不会重新生成随机选择。

具体错误点 #

• 随机值生成语句let randomValue = myArray[Math.floor(Math.random() * myArray.length)]定义在全局作用域，脚本加载时就执行完毕，不会重复触发
• computerPlay()函数内部没有编写随机计算逻辑，仅做固定值返回

修正后完整代码 #

const myArray = ['rock', 'paper', 'scissors']

function computerPlay() {
    // 每次调用函数时重新生成随机值，保证每轮选择不同
    const randomValue = myArray[Math.floor(Math.random() * myArray.length)]
    return randomValue;
}

function playRound(playerSelection, computerSelection) {
    // 兼容用户大小写输入
    playerSelection = playerSelection.toLowerCase()
    if (playerSelection == computerSelection) {
        console.log('It\'s a tie!')
        return
    } else if (
        (playerSelection == 'rock' && computerSelection == 'scissors') || 
        (playerSelection == 'paper' && computerSelection == 'rock') || 
        (playerSelection == 'scissors' && computerSelection == 'paper')
    ) {
        console.log('The human wins!');
        playerScore += 1;
        console.log(playerScore);
        return
    } else {
        console.log('The computer wins!');
        computerScore += 1;
        console.log(computerScore);
        return
    }
}

let playerScore = 0;
let computerScore = 0;
function game(){
    // 补全循环变量声明，避免全局污染
    for (let i = 0; i < 5; i++){
        const playerSelection = prompt('Choose your weapon');
        const computerSelection = computerPlay();
        playRound(playerSelection, computerSelection);
        console.log('Your score = ' + playerScore);
        console.log('Computer\'s score = ' + computerScore);
    }
}

game()

额外优化点 #

• 补全循环变量i的let声明，原代码未声明变量会泄露到全局作用域，易引发未知bug
• 新增玩家输入转小写逻辑，避免用户输入大写格式的选项时判定失效
• 移除parseInt(0)冗余写法，0本身就是数字类型，无需额外转换
• 移除不必要的console.log包裹，原代码console.log(playRound(...))和console.log(game())会额外打印undefined，因为两个函数没有返回值

内容的提问来源于stack exchange，提问作者Will