从if语句无法打开警报

Question

我正在制作剪刀石头布游戏，我希望警报来确定谁选择了什么以及谁赢得了比赛，但是警报不会弹出。 我发现有多个错误可以修复，并对其进行了重新检查，甚至进行了三重检查，但是警报仍然没有弹出？

这是三个功能之一（它们都是相似的）：

function rock() {
  var computerChoice = Math.random();
  if (computerChoice < 0.34) {
    computerChoice = "rock";
  } else if (computerChoice < 0.67) {
    computerChoice = "paper";
  } else {
    computerChoice = "scissors";
  }
}
if (computerChoice === "rock") {
   alert("Link and Computer both chose Rock! It's a Tie!");
} else if (computerChoice === "scissors") {
   alert("Link chose Rock and Computer chose Scissors! Computer took a heart of damage!");
} else {
   alert("Link chose Rock and Computer chose Paper! Link took a heart of damage!");
}
}

Answer 1

您无法返回警报。 Alert是一个方法调用。 删除警报前面的退货，警报将打开：

if(computerChoice === "rock"){
    alert("Link and Computer both chose Rock! It's a Tie!");
}

Answer 2

您不需要退货。 因此，更改此：

if(computerChoice === "rock"){
  return alert("Link and Computer both chose Rock! It's a Tie!");
}

对此：

if(computerChoice === "rock"){
  alert("Link and Computer both chose Rock! It's a Tie!");
}

Answer 3

我认为问题出在指示的行上：

function rock() {
  var computerChoice = Math.random();
  if (computerChoice < 0.34) {
    computerChoice = "rock";
  } else if (computerChoice < 0.67) {
    computerChoice = "paper";
  } else {
    computerChoice = "scissors";
  }
} // <-- I don't think you want this closing brace here
if (computerChoice === "rock") {
   alert("Link and Computer both chose Rock! It's a Tie!");
} else if (computerChoice === "scissors") {
   alert("Link chose Rock and Computer chose Scissors! Computer took a heart of damage!");
} else {
   alert("Link chose Rock and Computer chose Paper! Link took a heart of damage!");
}
}

我已经指出了右括号结束了rock()函数。 就目前而言， rock()函数实际上什么也没做。 它为局部变量随机分配一个值"rock" ， "paper"或"scissors" ，但是该函数在不使用该变量的情况下结束，因此该值丢失了。

然后，当首次将JavaScript加载到浏览器中时，其余代码将运行一次。 此时， computerChoice将是undefined ，因此您将收到一个JavaScript错误。

如果删除错误的括号，然后重新格式化代码，则会得到以下内容：

function rock() {
  var computerChoice = Math.random();
  if (computerChoice < 0.34) {
    computerChoice = "rock";
  } else if (computerChoice < 0.67) {
    computerChoice = "paper";
  } else {
    computerChoice = "scissors";
  }

  if (computerChoice === "rock") {
     alert("Link and Computer both chose Rock! It's a Tie!");
  } else if (computerChoice === "scissors") {
     alert("Link chose Rock and Computer chose Scissors! Computer took a heart of damage!");
  } else {
     alert("Link chose Rock and Computer chose Paper! Link took a heart of damage!");
  }
}

我多次运行了此功能。 每次它随机警告三个消息之一。

Answer 4

这有效并且使用较少的弯路到达那里:)

function rock() {
  var replies = new Array(
    'Link and Computer both chose Rock! It\'s a Tie!',
    'Link chose Rock and Computer chose Scissors! Computer took a heart of damage!',
    'Link chose Rock and Computer chose Paper! Link took a heart of damage!');
  alert(replies[Math.floor(replies.length * Math.random())]);
}

澄清：Math.random（）返回[0..1>
replies.length * Math.random（）返回[0..3>
Math.floor（replies.length * Math.random（））返回0、1或2。