---
id: 56533eb9ac21ba0edf2244e2
title: Caesars Cipher
challengeType: 5
isRequired: true
videoUrl: ''
localeTitle: 凯撒密码
---
## Description
最简单和最广为人知的密码之一是Caesar cipher ，也称为shift cipher 。在shift cipher中，字母的含义被移动一些设定量。一种常见的现代用途是ROT13密码，其中字母的值移动了13个位置。因此'A'''N'，'B'''O'等等。编写一个函数，它将ROT13编码的字符串作为输入并返回一个已解码的字符串。所有字母都是大写的。不要转换任何非字母字符（即空格，标点符号），但要传递它们。如果卡住，请记得使用Read-Search-Ask 。尝试配对程序。编写自己的代码。
## Instructions
## Tests
```yml
tests:
- text: rot13("SERR PBQR PNZC")应解码为FREE CODE CAMP
testString: 'assert(rot13("SERR PBQR PNZC") === "FREE CODE CAMP", "rot13("SERR PBQR PNZC") should decode to FREE CODE CAMP");'
- text: rot13("SERR CVMMN!")应该解码为FREE PIZZA! rot13("SERR CVMMN!") FREE PIZZA!
testString: 'assert(rot13("SERR CVMMN!") === "FREE PIZZA!", "rot13("SERR CVMMN!") should decode to FREE PIZZA!");'
- text: rot13("SERR YBIR?")应解码为FREE LOVE?
testString: 'assert(rot13("SERR YBIR?") === "FREE LOVE?", "rot13("SERR YBIR?") should decode to FREE LOVE?");'
- text: rot13("GUR DHVPX OEBJA SBK WHZCF BIRE GUR YNML QBT.")应该在rot13("GUR DHVPX OEBJA SBK WHZCF BIRE GUR YNML QBT.")解码到THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG.
testString: 'assert(rot13("GUR DHVPX OEBJA SBK WHZCF BIRE GUR YNML QBT.") === "THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG.", "rot13("GUR DHVPX OEBJA SBK WHZCF BIRE GUR YNML QBT.") should decode to THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG.");'
```
## Challenge Seed
```js
function rot13(str) { // LBH QVQ VG!
return str;
}
// Change the inputs below to test
rot13("SERR PBQR PNZC");
```
## Solution
```js
// solution required
```