JavaScript石头剪刀布游戏分数显示undefined的问题求助

核心问题1：函数参数覆盖全局变量 #

你的playGame函数定义了playerScore和computerScore作为参数，这会创建局部变量，直接覆盖全局作用域中声明的同名变量。而你调用playGame()时没传任何参数，这两个局部变量默认值是undefined，所以循环内打印的分数全是undefined。

核心问题2：playGame无返回值导致最终输出undefined #

最后一行console.log(playGame())会打印函数的返回值，但你的playGame函数没有写return语句，JS函数默认返回undefined，所以会输出这个结果。

修复步骤 #

步骤1：移除playGame的参数 #

删掉函数定义里的参数，让函数直接使用全局的分数变量：

function playGame() { // 移除括号里的playerScore和computerScore参数
    for (let i = 0; i < 5; i++){
        let computerSelection = getComputerChoice();
        let playerSelection = "Rock";
        console.log(playRound(playerSelection, computerSelection));
        console.log(`Player: ${playerScore}\nComputer: ${computerScore}`);
    }
}

步骤2：调整最终调用方式 #

直接调用playGame()就行，不用用console.log包裹，函数内部已经有打印逻辑：

playGame(); // 替换原来的console.log(playGame())

可选优化：避免全局变量（进阶） #

如果不想用全局变量，可以把分数作为函数内部状态，通过闭包管理，封装性更好：

function playGame() {
    let playerScore = 0;
    let computerScore = 0;

    function playRound(playerSelection, computerSelection) {
        if (playerSelection === computerSelection) {
            return "Draw!";
        }
        else if (playerSelection.toLowerCase() === "rock" && computerSelection === "Paper") {
            computerScore++;
            return ("Computer Wins!");
        }
        else if (playerSelection.toLowerCase() === "rock" && computerSelection === "Scissors") {
            playerScore++;
            return ("You Win!");
        }
        else if (playerSelection.toLowerCase() === "paper" && computerSelection === "Rock") {
            playerScore++;
            return ("You Win!");
        }
        else if (playerSelection.toLowerCase() === "paper" && computerSelection === "Scissors") {
            computerScore++;
            return ("Computer Wins!");
        }
        else if (playerSelection.toLowerCase() === "scissors" && computerSelection === "Rock") {
            computerScore++;
            return ("Computer Wins!");
        }
        else {
            return ("You Win!");
        }
    }

    for (let i = 0; i < 5; i++){
        let computerSelection = getComputerChoice();
        let playerSelection = "Rock";
        console.log(playRound(playerSelection, computerSelection));
        console.log(`Player: ${playerScore}\nComputer: ${computerScore}`);
    }
}

playGame();

内容的提问来源于stack exchange，提问作者NyPa-32