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id	title	challengeType	videoUrl	forumTopicId	dashedName
56533eb9ac21ba0edf2244e0	用一個 Switch 語句來替代多個 if else 語句	1	https://scrimba.com/c/c3JE8fy	18266	replacing-if-else-chains-with-switch

--description--

如果你有多個選項需要選擇，switch 語句寫起來會比多個串聯的 if/else if 語句容易些。譬如:

if (val === 1) {
  answer = "a";
} else if (val === 2) {
  answer = "b";
} else {
  answer = "c";
}

可以被下面替代：

switch (val) {
  case 1:
    answer = "a";
    break;
  case 2:
    answer = "b";
    break;
  default:
    answer = "c";
}

--instructions--

把串聯的 if/else if 語句改成 switch 語句。

--hints--

不要使用 else 表達式。

assert(!/else/g.test(code));

不要使用 if 表達式。

assert(!/if/g.test(code));

你應該有至少 4 個 break 表達式。

assert(code.match(/break/g).length >= 4);

chainToSwitch("bob") 應該是字符串 Marley

assert(chainToSwitch('bob') === 'Marley');

chainToSwitch(42) 應該是字符串 The Answer

assert(chainToSwitch(42) === 'The Answer');

chainToSwitch(1) 應該是字符串 There is no #1

assert(chainToSwitch(1) === 'There is no #1');

chainToSwitch(99)應該爲 Missed me by this much!。

assert(chainToSwitch(99) === 'Missed me by this much!');

chainToSwitch(7) 應該是字符串 Ate Nine

assert(chainToSwitch(7) === 'Ate Nine');

chainToSwitch("John") 應該爲 "" (empty string)。

assert(chainToSwitch('John') === '');

chainToSwitch(156) 應該爲 "" (empty string)。

assert(chainToSwitch(156) === '');

--seed--

--seed-contents--

function chainToSwitch(val) {
  let answer = "";
  // Only change code below this line

  if (val === "bob") {
    answer = "Marley";
  } else if (val === 42) {
    answer = "The Answer";
  } else if (val === 1) {
    answer = "There is no #1";
  } else if (val === 99) {
    answer = "Missed me by this much!";
  } else if (val === 7) {
    answer = "Ate Nine";
  }

  // Only change code above this line
  return answer;
}

chainToSwitch(7);

--solutions--

function chainToSwitch(val) {
  let answer = "";

  switch (val) {
    case "bob":
      answer = "Marley";
      break;
    case 42:
      answer = "The Answer";
      break;
    case 1:
      answer = "There is no #1";
      break;
    case 99:
      answer = "Missed me by this much!";
      break;
    case 7:
      answer = "Ate Nine";
  }
  return answer;
}

2.6 KiB Raw Blame History