129 lines
2.1 KiB
Markdown
129 lines
2.1 KiB
Markdown
---
|
||
id: 56533eb9ac21ba0edf2244de
|
||
title: 在 Switch 语句中添加默认选项
|
||
challengeType: 1
|
||
videoUrl: 'https://scrimba.com/c/c3JvVfg'
|
||
forumTopicId: 16653
|
||
dashedName: adding-a-default-option-in-switch-statements
|
||
---
|
||
|
||
# --description--
|
||
|
||
在 `switch` 语句中你可能无法用 case 来指明所有情况，这时我们可以添加 default 语句来解决这个问题。在无法找到匹配的 case 时，default 语句就会执行。这非常类似于 if/else 语句中的 else 语句。
|
||
|
||
注意，`default` 语句应该在所有的 `case` 之后。
|
||
|
||
```js
|
||
switch (num) {
|
||
case value1:
|
||
statement1;
|
||
break;
|
||
case value2:
|
||
statement2;
|
||
break;
|
||
...
|
||
default:
|
||
defaultStatement;
|
||
break;
|
||
}
|
||
```
|
||
|
||
# --instructions--
|
||
|
||
请实现根据下面的条件来设置 `answer` 的 `switch` 语句：
|
||
`"a"` - "apple"
|
||
`"b"` - "bird"
|
||
`"c"` - "cat"
|
||
`default` - "stuff"
|
||
|
||
# --hints--
|
||
|
||
`switchOfStuff("a")` 的值应为 "apple"。
|
||
|
||
```js
|
||
assert(switchOfStuff('a') === 'apple');
|
||
```
|
||
|
||
`switchOfStuff("b")` 的值应为 "bird"。
|
||
|
||
```js
|
||
assert(switchOfStuff('b') === 'bird');
|
||
```
|
||
|
||
`switchOfStuff("c")` 的值应为 "cat"。
|
||
|
||
```js
|
||
assert(switchOfStuff('c') === 'cat');
|
||
```
|
||
|
||
`switchOfStuff("d")` 的值应为 "stuff"。
|
||
|
||
```js
|
||
assert(switchOfStuff('d') === 'stuff');
|
||
```
|
||
|
||
`switchOfStuff("4")` 的值应为 "stuff"。
|
||
|
||
```js
|
||
assert(switchOfStuff(4) === 'stuff');
|
||
```
|
||
|
||
不应使用 `if` 或 `else` 语句。
|
||
|
||
```js
|
||
assert(!/else/g.test(code) || !/if/g.test(code));
|
||
```
|
||
|
||
应有一个 `default` 语句。
|
||
|
||
```js
|
||
assert(switchOfStuff('string-to-trigger-default-case') === 'stuff');
|
||
```
|
||
|
||
应至少有 3 个 `break` 语句。
|
||
|
||
```js
|
||
assert(code.match(/break/g).length > 2);
|
||
```
|
||
|
||
# --seed--
|
||
|
||
## --seed-contents--
|
||
|
||
```js
|
||
function switchOfStuff(val) {
|
||
var answer = "";
|
||
// Only change code below this line
|
||
|
||
|
||
|
||
// Only change code above this line
|
||
return answer;
|
||
}
|
||
|
||
switchOfStuff(1);
|
||
```
|
||
|
||
# --solutions--
|
||
|
||
```js
|
||
function switchOfStuff(val) {
|
||
var answer = "";
|
||
|
||
switch(val) {
|
||
case "a":
|
||
answer = "apple";
|
||
break;
|
||
case "b":
|
||
answer = "bird";
|
||
break;
|
||
case "c":
|
||
answer = "cat";
|
||
break;
|
||
default:
|
||
answer = "stuff";
|
||
}
|
||
return answer;
|
||
}
|
||
```
|