Question

编写动态代码时遇到问题。我正在进行javascript编程课程，而且我在一项任务的最后部分遇到了一些困难。

练习8.2

使用默认值扩展switch-case语句。结果应该     be＆＃39;那是一种未知的水果。＆＃39;当变量＆＃39; myFruit＆＃39;有一个未知数     值。回答结果，其中myFruit = pear＆＃39;。

在下面编写代码并将答案放入变量ANSWER。

var myFruit = "pear";
switch (myFruit) {
  case "banana":
  console.log("The banana is yellow.");
  break;
  case "apple":
  console.log("The apple is green.");
  break;
  case "kiwi":
  console.log("The kiwi is green.");
  break;
  case "plum":
  console.log("The plum is purple");
  break;
  default:
  console.log("That is an unknown fruit.");
  break;}

如何在变量中表达此结果？

我试着这样写：

var result = switch (myFruit);

但这不起作用。

Answer 1

您可以声明result变量，并在switch语句的情况下，而不是console.log ging结果，您可以将值赋给result变量，如下所示：< / p>

var myFruit = "pear";
var result;
switch (myFruit) {
  case "banana":
      result = "The banana is yellow.";
      break;
  case "apple":
      result = "The apple is green.";
      break;
  case "kiwi":
      result = "The kiwi is green.";
      break;
  case "plum":
      result = "The plum is purple";
      break;
  default:
      result = "That is an unknown fruit.";
      break;
}

http://jsfiddle.net/uqxtmc25/

Answer 2

我不会为您写出所有代码，但请指出正确的方向。您需要在变量中设置文本并将其返回：

switch ..

    case "something":
        var message = "Your message here.";
        break;

...

一旦您的开关设置了值，您就可以根据需要使用它。

您不能像操作一样使用switch语句从switch语句返回值。

Answer 3

你不能像var result = switch (myFruit);那样调用switch语句，它不是一个函数。您必须将所有开关案例代码移动到一个函数中：

function mySwitchCase(fruit){
    var returnResult='';
    switch (fruit) {
        case "banana":
           returnResult="The banana is yellow.";
            break;
        case "apple":
            returnResult="The apple is green.";
            break;
        case "kiwi":
            returnResult"The kiwi is green.";
            break;
        case "plum":
            returnResult"The plum is purple";
            break;
        default:
            returnResult"That is an unknown fruit.";
            break;
    }
    return returnResult;
}

然后你可以这样称呼它：

var result = mySwitchCase(myFruit);

Answer 4

您可以将结果保存在变量answer中，然后使用该变量打印出结果;

function fruitSwitcher (myFruit) {
    var answer = "That is an unknown fruit.";
    switch (myFruit) {
      case "banana":
      answer = "The banana is yellow.";
      break;
      case "apple":
      answer = "The apple is green.";
      break;
      case "kiwi":
      answer ="The kiwi is green.";
      break;
      case "plum":
      answer = "The plum is purple";
      break;
      default: 
      // no really needed
      answer ="That is an unknown fruit.";
      break;
     }

     return answer;
}

var myFruit = "pear";
var answer = fruitSwitcher(myFruit);
console.log(answer); //That is an unknown fruit.

上一代码中的默认情况是多余的，因为变量answer初始化为默认值。如果传入输入中的未知果实，则没有任何开关案例与之匹配，因此answer变量永远不会更改值，函数将返回默认值。

如何在变量中写出我的答案？

4 个答案: