[JS][7kyu] How Many Lonely Letters?

codewars/7kyu/how-many-lonely-letters/koronya.js

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+// [JS][7kyu] How Many Lonely Letters?
+// how-many-lonely-letters
+// https://www.codewars.com/kata/69cda5b85599f307742ce70a/train/javascript
+
+const countLonelyLetters = (text) => {
+  const strMap = new Map()
+  const arr = text
+    .split('')
+    .filter((letter) => /[a-zA-Z]/.test(letter))
+    .map((letter) => letter.toLowerCase().charCodeAt(0))
+    .forEach((code) => {
+      strMap.set(code, (strMap.get(code) || 0) + 1)
+    })
+  let count = 0
+  strMap.forEach((value, key) => {
+    if (value === 1 && !strMap.has(key - 1) && !strMap.has(key + 1)) {
+      count += 1
+    }
+  })
+
+  return count
+}
+
+countLonelyLetters('ad') === 2
+countLonelyLetters('abc') === 0
+countLonelyLetters('Hello, World!') === 3
+countLonelyLetters('A-dA') === 1
+countLonelyLetters('zz') === 0
+
+countLonelyLetters('') === 0
+countLonelyLetters('123 !!!') === 0
+countLonelyLetters('bdfhj') === 5
+countLonelyLetters('a') === 1
+countLonelyLetters('z') === 1
+countLonelyLetters('iiiaii`ii') === 1
+countLonelyLetters('iiiziii{iii') === 1
+countLonelyLetters('iiiAiii@ii') === 1
+countLonelyLetters('iiiZiii[iii') === 1
+
+countLonelyLetters('Aa') === 0
+countLonelyLetters('B!d') === 2
+countLonelyLetters('C-c?e') === 1