JavaScript 错误：“竞赛”不是函数答案

【问题标题】：JavaScript error: 'contest' is not a functionJavaScript 错误：“竞赛”不是函数
【发布时间】：2020-10-16 17:53:22
【问题描述】：

我正在用 JavaScript 制作一个简单的石头剪刀布游戏，但我一直遇到一个错误，当我调用一个函数时，它总是返回它不是一个。任何帮助，将不胜感激！我确定我只是输入了错误的位置，或者我没有正确传递变量。或者我尝试过移动它并且尝试不将变量传递给它，但它一直给我相同的错误代码。

var playGame = function() {
  var playerChoice = window.prompt("Choose your weapon! Enter r for Rock, p for paper, or s for Scissors.");
  console.log(playerChoice)
  switch (playerChoice) {
    case "r":
      console.log("Player chooses Rock!");
      break;
    case "p":
      console.log("Player chooses Paper!");
      break;
    case "s":
      console.log("Player chooses Scissors!");
      break;
    default:
      window.alert("You did not pick a valid option. Try again.");
      playGame();
      break;
  };
  var randomNum = Math.floor(Math.random() * 3 + 1);
  console.log(randomNum);
  var compChoice = "";
  switch (randomNum) {
    case 1:
      compChoice = "r";
      console.log(compChoice);
      break;
    case 2:
      compChoice = "p";
      console.log(compChoice);
      break;
    case 3:
      compChoice = "s"
      console.log(compChoice);
      break;
  };
  contest(playerChoice, compChoice);
};

var playConfirm = window.confirm("Would you like to play Rock, Paper, Scissors?");
if (playConfirm) {
  playGame();
} else {
  alert("Ok, maybe next time. Have a nice day!");
}
var contest = function(pChoice, cChoice) {
  // for () {
  switch (pChoice, cChoice) {
    case (pChoice === cChoice):
      window.alert("It's a tie!");
      // playAgain();
      break;
    case (pChoice = "r") && (cChoice = "p"):
      window.alert("I won! Paper covers rock!");
      // playAgain();
      break;
    case (pChoice = "r") && (cChoice = "s"):
      window.alert("You won! Rock crushes scissors!");
      // playAgain();
      break;
    case (pChoice = "p") && (cChoice = "r"):
      window.alert("You won! Paper covers rock!");
      // playAgain();
      break;
    case (pChoice = "p") && (cChoice = "s"):
      window.alert("I won! Scissors cuts paper!");
      // playAgain();
      break;
    case (pChoice = "s") && (cChoice = "r"):
      window.alert("I won! Rock crushes scissors!");
      // playAgain();
      break;
    case (pChoice = "s") && (cChoice = "p"):
      window.alert("You won! Scissors cuts paper!");
      // playAgain();
      break;
  }
};

【问题讨论】：

错误出现在哪里？
您收到错误是因为您在将函数分配给 contest 之前调用了 playGame（它调用了 contest）。

标签： javascript function loops

【解决方案1】：

这是因为你在定义之前使用了contest函数。

如果在使用前移动contest函数定义，它会起作用。

var contest = function (pChoice, cChoice) {
  // for () {
  switch (pChoice, cChoice) {
    case (pChoice === cChoice):
      window.alert("It's a tie!");
      // playAgain();
      break;
    case (pChoice = "r") && (cChoice = "p"):
      window.alert("I won! Paper covers rock!");
      // playAgain();
      break;
    case (pChoice = "r") && (cChoice = "s"):
      window.alert("You won! Rock crushes scissors!");
      // playAgain();
      break;
    case (pChoice = "p") && (cChoice = "r"):
      window.alert("You won! Paper covers rock!");
      // playAgain();
      break;
    case (pChoice = "p") && (cChoice = "s"):
      window.alert("I won! Scissors cuts paper!");
      // playAgain();
      break;
    case (pChoice = "s") && (cChoice = "r"):
      window.alert("I won! Rock crushes scissors!");
      // playAgain();
      break;
    case (pChoice = "s") && (cChoice = "p"):
      window.alert("You won! Scissors cuts paper!");
      // playAgain();
      break;
  }
};

var playGame = function() {
  var playerChoice = window.prompt("Choose your weapon! Enter r for Rock, p for paper, or s for Scissors.");
  console.log(playerChoice)
  switch (playerChoice) {
    case "r":
      console.log("Player chooses Rock!");
      break;
    case "p":
      console.log("Player chooses Paper!");
      break;
    case "s":
      console.log("Player chooses Scissors!");
      break;
    default:
      window.alert("You did not pick a valid option. Try again.");
      playGame();
      break;
  };
  var randomNum = Math.floor(Math.random() * 3 + 1);
  console.log(randomNum);
  var compChoice = "";
  switch (randomNum) {
    case 1:
      compChoice = "r";
      console.log(compChoice);
      break;
    case 2:
      compChoice = "p";
      console.log(compChoice);
      break;
    case 3:
      compChoice = "s"
      console.log(compChoice);
      break;
  };
  contest(playerChoice, compChoice);
};

var playConfirm = window.confirm("Would you like to play Rock, Paper, Scissors?");
if (playConfirm) {
  playGame();
} else {
  alert("Ok, maybe next time. Have a nice day!");
}

【讨论】：

我在底部添加了我的答案，这也有效。那么我想知道为什么要移动window.confirm 固定呢？
这取决于函数调用的点。当您将playConfirm 放在contest 上方时，直到用户在提示符上输入，contest 定义部分将不会被调用。所以它将是未定义的并且无法调用。但是在您将playConfirm 移动到比赛下之后，这意味着在比赛定义运行之后，prompt 将被显示。所以这个函数就存在了。
@4156：你的答案和这个完全一样。您不仅移动了window.confirm，还移动了playGame() 函数调用。将这些行“移至底部”并将 context 声明“移至顶部”会产生相同的结果。

【解决方案2】：

由于某种原因，移动了

var playConfirm = window.confirm("Would you like to play Rock, Paper, Scissors?");
if (playConfirm) {
  playGame();
} else {
  alert("Ok, maybe next time. Have a nice day!");
}

到底部修复它，可能与它如何调用函数有关？

【讨论】：