106 lines
1.6 KiB
Markdown
106 lines
1.6 KiB
Markdown
---
|
|
id: 56533eb9ac21ba0edf2244e0
|
|
title: 用一个 Switch 语句来替代多个 if else 语句
|
|
challengeType: 1
|
|
videoUrl: 'https://scrimba.com/c/c3JE8fy'
|
|
forumTopicId: 18266
|
|
---
|
|
|
|
# --description--
|
|
|
|
如果你有多个选项需要选择，`switch`语句写起来会比多个串联的`if`/`if else`语句容易些，譬如:
|
|
|
|
```js
|
|
if (val === 1) {
|
|
answer = "a";
|
|
} else if (val === 2) {
|
|
answer = "b";
|
|
} else {
|
|
answer = "c";
|
|
}
|
|
```
|
|
|
|
可以被下面替代：
|
|
|
|
```js
|
|
switch(val) {
|
|
case 1:
|
|
answer = "a";
|
|
break;
|
|
case 2:
|
|
answer = "b";
|
|
break;
|
|
default:
|
|
answer = "c";
|
|
}
|
|
```
|
|
|
|
# --instructions--
|
|
|
|
把串联的`if`/`if else`语句改成`switch`语句。
|
|
|
|
# --hints--
|
|
|
|
不要使用`else`表达式。
|
|
|
|
```js
|
|
assert(!/else/g.test(code));
|
|
```
|
|
|
|
不要使用`if`表达式。
|
|
|
|
```js
|
|
assert(!/if/g.test(code));
|
|
```
|
|
|
|
你应该有至少 4 个`break`表达式。
|
|
|
|
```js
|
|
assert(code.match(/break/g).length >= 4);
|
|
```
|
|
|
|
`chainToSwitch("bob")`应该为 "Marley"。
|
|
|
|
```js
|
|
assert(chainToSwitch('bob') === 'Marley');
|
|
```
|
|
|
|
`chainToSwitch(42)`应该为 "The Answer"。
|
|
|
|
```js
|
|
assert(chainToSwitch(42) === 'The Answer');
|
|
```
|
|
|
|
`chainToSwitch(1)`应该为 "There is no
|
|
|
|
```js
|
|
assert(chainToSwitch(1) === 'There is no #1');
|
|
```
|
|
|
|
`chainToSwitch(99)`应该为 "Missed me by this much!"。
|
|
|
|
```js
|
|
assert(chainToSwitch(99) === 'Missed me by this much!');
|
|
```
|
|
|
|
`chainToSwitch(7)`应该为 "Ate Nine"。
|
|
|
|
```js
|
|
assert(chainToSwitch(7) === 'Ate Nine');
|
|
```
|
|
|
|
`chainToSwitch("John")`应该为 "" (empty string)。
|
|
|
|
```js
|
|
assert(chainToSwitch('John') === '');
|
|
```
|
|
|
|
`chainToSwitch(156)`应该为 "" (empty string)。
|
|
|
|
```js
|
|
assert(chainToSwitch(156) === '');
|
|
```
|
|
|
|
# --solutions--
|
|
|