[JS][7kyu] You Complete Me

codewars/7kyu/you-complete-me/koronya.js

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+// [JS][7kyu] You Complete Me
+// you-complete-me
+// https://www.codewars.com/kata/63967eb85e54bd00237d2201/train/javascript
+
+const getReverseString = (str) => str.split('').reverse().join('')
+const isSameCharString = (str) => new Set(str.split('')).size === 1
+
+const complete = (str) => {
+  if (isSameCharString(str)) {
+    return str + str[0]
+  }
+  const strLength = str.length
+  const reverseStr = getReverseString(str)
+
+  let sameIndex = 0
+  for (let i = 0; i < strLength; i += 1) {
+    str.slice(i)
+    reverseStr.slice(0, strLength - i)
+    if (str.slice(i) === reverseStr.slice(0, strLength - i)) {
+      sameIndex = i
+      break
+    }
+  }
+
+  const appendStr = sameIndex === 0 ? str.slice(1) : getReverseString(str.slice(0, sameIndex))
+  return str + appendStr
+}
+
+// complete('Baa') === 'BaaB'
+// complete('aaB') === 'aaBaa'
+// complete('x') === 'xx'
+// complete('aaBB') === 'aaBBaa'
+// complete('aOOa') === 'aOOaOOa'
+// complete('xyz') === 'xyzyx'
+// complete('AaaaA') === 'AaaaAaaaA'
+// complete('abab') === 'ababa'
+// complete('bbbbbbbbbbbbb')