### [ROT13](https://www.codewars.com/kata/52223df9e8f98c7aa7000062)****
- 知識點：String.fromCharCode()、正則、字串比大小
:::spoiler 解法
``` javascript=
function rot13(str) {
const arr = str.split("");
const result = [];
arr.forEach((e) => {
const upperLetter = e.toUpperCase().charCodeAt(0);
upperLetter >= 65 && upperLetter <= 77
? result.push(String.fromCharCode(e.charCodeAt(0) + 13))
: upperLetter >= 78 && upperLetter <= 90
? result.push(String.fromCharCode(e.charCodeAt(0) - 13))
: result.push(e);
});
return result.join("");
}
console.log(rot13("EBG13 rknzcyr."));
```
- 字串可以直接來比大小，會自動用 ASCII 去判斷大小
```javascript=
console.log("a" <= "m"); // true
console.log("r" <= "m"); // false
console.log("你好" <= "哈囉"); // true
```
- `/[a-z]/ig` i 表示不分區分大小寫
```javascript=
function rot13(str) {
return str.replace(/[a-z]/ig, function(x){
return String.fromCharCode(x.charCodeAt(0) + (x.toLowerCase() <= 'm' ? 13: -13));
});
}
```
:::
### [The Hashtag Generator](https://www.codewars.com/kata/52449b062fb80683ec000024)****
- 知識點：replaceAll()+regex、every()
:::spoiler 解法
``` javascript=
function generateHashtag(str) {
if (!str || str.split("").every((e) => e == " ")) return false;
const result = `#${str
.replaceAll(/(^[a-z]|\s[a-z])/g, (match) => match.toUpperCase())
.replaceAll(" ", "")}`;
return result.length <= 140 ? result : false;
}
console.log(generateHashtag(" ".repeat(200)));
```
:::
### [Scramblies](https://www.codewars.com/kata/55c04b4cc56a697bb0000048)****
- 知識點：
:::spoiler 解法
``` javascript=
function scramble(str1, str2) {
const letter = str1.split("").reduce((obj, c) => {
obj[c] ? obj[c]++ : (obj[c] = 1);
return obj;
}, {});
let result = true;
for (let i = 0; i < str2.length; i++) {
if (letter[str2[i]]) {
letter[str2[i]]--;
} else {
result = false;
}
}
return result;
}
scramble("cedewaraaossoqqyt", "codewars");
```
```javascript=
function scramble(str1, str2) {
let occurences = str1.split("").reduce((arr, cur) => { arr[cur] ? arr[cur]++ : arr[cur] = 1; return arr; }, {});
return str2.split("").every((character) => --occurences[character] >= 0);
}
```
:::
### [title]()**
- 知識點：
:::spoiler 解法
``` javascript=
```
:::
{"title":"Codewars 5kyu","description":"知識點：","contributors":"[{\"id\":\"65ef09e4-76a5-4ffa-8afd-4e2465c6240e\",\"add\":2262,\"del\":11}]"}