116 lines
2.7 KiB
Markdown
116 lines
2.7 KiB
Markdown
---
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id: 56533eb9ac21ba0edf2244de
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title: Adding a Default Option in Switch Statements
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challengeType: 1
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videoUrl: 'https://scrimba.com/c/c3JvVfg'
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forumTopicId: 16653
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localeTitle: 在 Switch 语句中添加默认选项
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---
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## Description
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<section id='description'>
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在<code>switch</code>语句中你可能无法用 case 来指定所有情况，这时你可以添加 default 语句。当再也找不到 case 匹配的时候 default 语句会执行，非常类似于 if/else 组合中的 else 语句。
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<code>default</code>语句应该是最后一个 case。
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```js
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switch (num) {
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case value1:
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statement1;
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break;
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case value2:
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statement2;
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break;
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...
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default:
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defaultStatement;
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break;
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}
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```
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</section>
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## Instructions
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<section id='instructions'>
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写一个 switch 语句，根据下面的条件来设置<code>answer</code>的switch语句：<br><code>"a"</code> - "apple"<br><code>"b"</code> - "bird"<br><code>"c"</code> - "cat"<br><code>default</code> - "stuff"
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</section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: <code>switchOfStuff("a")</code>应该有一个值为 "apple"。
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testString: assert(switchOfStuff("a") === "apple");
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- text: <code>switchOfStuff("b")</code>应该有一个值为 "bird"。
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testString: assert(switchOfStuff("b") === "bird");
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- text: <code>switchOfStuff("c")</code>应该有一个值为 "cat"。
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testString: assert(switchOfStuff("c") === "cat");
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- text: <code>switchOfStuff("d")</code>应该有一个值为 "stuff"。
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testString: assert(switchOfStuff("d") === "stuff");
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- text: <code>switchOfStuff(4)</code>应该有一个值为 "stuff"。
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testString: assert(switchOfStuff(4) === "stuff");
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- text: 不能使用任何<code>if</code>或<code>else</code>表达式。
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testString: assert(!/else/g.test(code) || !/if/g.test(code));
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- text: 你应该有一个<code>default</code>表达式。
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testString: assert(switchOfStuff("string-to-trigger-default-case") === "stuff");
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- text: 你应该有至少 3 个<code>break</code>表达式。
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testString: assert(code.match(/break/g).length > 2);
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='js-seed'>
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```js
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function switchOfStuff(val) {
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var answer = "";
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// Only change code below this line
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// Only change code above this line
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return answer;
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}
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// Change this value to test
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switchOfStuff(1);
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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function switchOfStuff(val) {
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var answer = "";
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switch(val) {
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case "a":
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answer = "apple";
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break;
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case "b":
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answer = "bird";
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break;
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case "c":
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answer = "cat";
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break;
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default:
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answer = "stuff";
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}
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return answer;
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}
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```
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</section>
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