javascript - Noobish JavaScript 嵌套 If-Else 语句帮助/建议/指针/YouNameIt

Question

我刚刚开始学习 JavaScript(实际上是今天)，我非常感谢有关嵌套 if-else 语句的一些帮助。我想我应该编写一个简单的程序来练习，似乎 if block 中的每个 if-else 语句都会执行，无论我输入哪个参数。任何指针甚至您注意到与问题无关的东西手受到赞赏。再次感谢。我的代码如下。

编辑:我现在已经明白了，并且认识到了我的方式的错误。感谢所有如此迅速发表评论和提供建议的人。

var playerOne = prompt('Choose rock, paper, or scissors'); 
var playerTwo = prompt('Choose rock, paper, or scissors'); 

var fight = function (playerOne, playerTwo)
{ 
    if( playerOne == 'rock' || 'Rock')
    { 
        if (playerTwo == 'paper' || 'Paper')
        {
            alert('Player Two Wins!');
        }
        else if (playerTwo == 'rock' || 'Rock')
        {
            alert('Tie!');
        }
        else
        {
            alert('Player One wins!');
        }
    }

        if(playerOne == 'paper' || 'Paper')
        { 
            if (playerTwo == 'paper' || 'Paper')
            {
                alert('Tie!');
            }
            else if (playerTwo == 'rock' || 'Rock')
            {
                alert('Player One Wins!'); 
            }
            else 
            {
                alert('Player Two  wins!');
            }
        }

        if (playerOne == 'scissors' || 'Scissors')
        {
             if (playerTwo == 'paper' || 'Paper')
             {
                alert('Player One Wins!');
             }
            else if (playerTwo == 'rock' || 'Rock')
            {
                alert('Player Two Wins!');
            }
            else
            {
                alert('Tie!');
            }
        }

};

fight(playerOne, playerTwo); 

Answer 1

正如一些人指出的那样，您的 if 语句需要采用以下形式:

if (playerOne == 'paper' || playerOne == 'Paper')

或者更简洁:

if (playerOne.toLowerCase() == 'paper')

问题是 playerOne == 'paper' || “Paper” 将始终返回“Truthy”值(有关 Truthy 和 Falsy 值的更多详细信息，请参阅 http://11heavens.com/falsy-and-truthy-in-javascript)。

顺便说一句，虽然多个 if 语句绝对没有任何问题，但如果我编写这个练习，我的方式将涉及更少的 if 语句(看起来有点像这个:

var playerOne = prompt('Choose rock, paper, or scissors');
var playerTwo = prompt('Choose rock, paper, or scissors');
var fists = {
    "rock": {
        "beats": "scissors",
        "loses": "paper"
    },
    "paper": {
        "beats": "rock",
        "loses": "scissors"
    },
    "scissors": {
        "beats": "paper",
        "loses": "rock"
    }
}

var fight = function (playerOne, playerTwo) {
    playerOne = playerOne.toLowerCase();
    playerTwo = playerTwo.toLowerCase();

    if (fists[playerOne] === undefined || fists[playerTwo] === undefined) {
        alert('Someone threw an unknown fist!');
    } else if (fists[playerOne].beats === playerTwo) {
        alert('Player One wins!');
    } else if (fists[playerTwo].beats === playerOne) {
        alert('Player Two Wins!');
    } else {
        alert('Tie!');
    }
};

fight(playerOne, playerTwo);

通过具体化石头/剪刀/布的组合，在我看来代码更容易阅读。