freeCodeCamp/curriculum/challenges/chinese/02-javascript-algorithms-and-data-structures/basic-javascript/use-bracket-notation-to-find-the-nth-to-last-character-in-a-string.md

id, challengeType, videoUrl, forumTopicId, title

id	challengeType	videoUrl	forumTopicId	title
bd7123c9c452eddfaeb5bdef	1	https://scrimba.com/c/cw4vkh9	18344	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

tests:
  - text: <code>secondToLastLetterOfLastName</code>应该是"c"。
    testString: assert(secondToLastLetterOfLastName === 'c');
  - text: 你需要使用<code>.length</code>获取倒数第二个字符。
    testString: assert(code.match(/\.length/g).length === 2);

Challenge Seed

// 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

(function(v){return v;})(secondToLastLetterOfLastName);

Solution

var firstName = "Ada";
var thirdToLastLetterOfFirstName = firstName[firstName.length - 3];

var lastName = "Lovelace";
var secondToLastLetterOfLastName = lastName[lastName.length - 2];