--- id: bd7123c9c452eddfaeb5bdef challengeType: 1 videoUrl: 'https://scrimba.com/c/cw4vkh9' forumTopicId: 18344 title: 使用方括号查找字符串中的第N个字符到最后一个字符 --- ## Description
我们既可以获取字符串的最后一个字符,也可以用获取字符串的倒数第N个字符。 例如,你可以这样firstName[firstName.length - 3]操作来获得var firstName = "Charles"字符串中的倒数第三个字符。
## Instructions
使用方括号来获得lastName字符串中的倒数第二个字符。 提示
如果你遇到困难了,不妨看看thirdToLastLetterOfFirstName变量是如何做到的。
## Tests
```yml tests: - text: secondToLastLetterOfLastName应该是"c"。 testString: assert(secondToLastLetterOfLastName === 'c'); - text: 你需要使用.length获取倒数第二个字符。 testString: assert(code.match(/\.length/g).length === 2); ```
## Challenge Seed
```js // Example var firstName = "Ada"; var thirdToLastLetterOfFirstName = firstName[firstName.length - 3]; // Setup var lastName = "Lovelace"; // Only change code below this line var secondToLastLetterOfLastName = lastName; ```
### After Test
```js (function(v){return v;})(secondToLastLetterOfLastName); ```
## Solution
```js var firstName = "Ada"; var thirdToLastLetterOfFirstName = firstName[firstName.length - 3]; var lastName = "Lovelace"; var secondToLastLetterOfLastName = lastName[lastName.length - 2]; ```