Question

我正在尝试让石头剪刀布成为计算机与人类玩家的比赛。我有函数 computerplay(); 从三个可能的字符串（“Rock”、“Paper”、“Scissors”）中生成随机值作为游戏匹配值的计算机选择。使用第三个函数 save(); 我允许玩家将他的选择输入到 HTML 表单中并尝试将其保存到 round();功能。

作为结果，我想得到变量 c 或 p 递增或打印字符串“draw”作为 round(); 获取存储在 x 中的计算机选择和变量玩家的玩家选择的指示。似乎 x 和 player 都附加了它们的值，但 round(); 函数没有接收到它。感谢您帮助解决。

function computerPlay() {
       const number = Math.floor(Math.random() * 1000);
        if (number % 3 === 0) {
                return 'Rock';
       }
        if (number % 3 === 1) {
                return 'Paper';
        }
        return 'Scissors';
}


var p = 0;
var c = 0;


 var x = computerPlay();
    var player;
      player = document.getElementById("player").value;
 document.write(x);
function round ( playerSelection = player, computerSelection =  x ) {

 document.write(player);
 document.write(x);
 
                 if (playerSelection == 'Rock' && computerSelection == 'Rock') {
           
                      
                      
                     document.write (p);
                     document.write (c); 
                    
                     document.write("draw"); 
                  }

                 else if (playerSelection == 'Rock' && computerSelection == 'Paper') {
           
                      
                     c++; 
                     document.write (p); 
                     document.write (c); 
                     document.write("comp"); 
                  }
           
                 else if (playerSelection == 'Rock' && computerSelection == 'Scissors') {
           
                      
                     p++;
                     document.write (p);  
                     document.write (c); 
                     document.write("player"); 
                  }
                 else if (playerSelection == 'Scissors' && computerSelection == 'Rock') {
           
                      
                     c++;
                     document.write (p);  
                     document.write (c); 
                     document.write("comp"); 
                  }
                else if (playerSelection == 'Scissors' && computerSelection == 'Paper') {
           
                      
                     p++; 
                     document.write (p);
                     document.write (c); 
                     document.write("player"); 
                  }

                else if (playerSelection == 'Scissors' && computerSelection == 'Scissors') {
           
                      
                     document.write (p);
                     document.write (c); 
                     document.write("draw"); 
                  }

                 else if (playerSelection == 'Paper' && computerSelection == 'Rock') {
           
                      
                     p++; 
                     document.write (p);
                     document.write (c); 
                     document.write("player"); 
                  }

                else if (playerSelection == 'Paper' && computerSelection == 'Scissors') {
           
                      
                     c++; 
                     document.write (p);
                     document.write (c); 
                     document.write("computer"); 
                  }

                 else if (playerSelection == 'Paper' && computerSelection == 'Paper') {
           
                      
                     document.write (p);
                     document.write (c); 
                     document.write("draw"); 
                  }
              }









  function save() {
      var player;
      player = document.getElementById("player").value;
       document.write (player);
       document.write(x);
       computerPlay();
       var x = computerPlay();
       round();
       

     

}



document.write (p); 
    document.write (c); 

if ( c == 5 ) {
    document.write (c); 
    document.write ('computer win');
}
else if ( p == 5 ) {
   document.write ('player win');
 }

<p id="demo"></p>

<form id="form">
  <input id="player" type="text" min="1" name="player">
  <button type="button" onclick="save();">Get Value</button>
</form>

Answer 1

在您的脚本中，您使用了两个都称为 player 的变量，这里有一个：

var x = computerPlay();
  var player; 
    player = document.getElementById("player").value;

这里有一个：

function save() {
  var player;
  player = document.getElementById("player").value;

第一个变量在脚本主体中声明，这意味着它具有“全局作用域”。相反，您在 save() 中定义的函数具有“函数作用域”（这意味着该函数体之外的任何人都看不到它）。

由于您不带参数调用 round()，它将使用默认值初始化它们，并从发生函数声明的作用域（在本例中为全局作用域）中获取这些值。由于全局 player 最初是空的并且您永远不会更改该变量，因此 round 将始终将其第一个参数作为空字符串。有多种方法可以“解决”这个问题：

直接在round()内部获取变量：

  function round(/* ... */) {
      player = document.get...

其实就是把参数传给函数：
```
  round(player);
```

更新 player 变量的值而不是创建一个新变量：

  var player;

  function save() {
      player = document.get...
      round();
  }

有关 JavaScript 范围规则的更多信息，请阅读 here

其他函数调用函数不起作用

1 个答案: