Added implementation for arbitrary base conversion

Conversions/ArbitraryBase.js

@@ -0,0 +1,45 @@
+/**
+* Converts a string from one base to other
+* @param {string} stringInBaseOne String in input base
+* @param {string} baseOneCharacters Character set for the input base
+* @param {string} baseTwoCharacters Character set for the output base
+* @returns {string}
+*/
+const convertArbitraryBase = (stringInBaseOne, baseOneCharacters, baseTwoCharacters) => {
+  if ([stringInBaseOne, baseOneCharacters, baseTwoCharacters].map(arg => typeof arg).some(type => type !== 'string')) {
+    throw new TypeError('Only string arguments are allowed')
+  }
+  [baseOneCharacters, baseTwoCharacters].forEach(baseString => {
+    const charactersInBase = [...baseString]
+    if (charactersInBase.length !== new Set(charactersInBase).size) {
+      throw new TypeError('Duplicate characters in character set are not allowed')
+    }
+  })
+  const reversedStringOneChars = [...stringInBaseOne].reverse()
+  const stringOneBase = baseOneCharacters.length
+  let value = 0
+  let placeValue = 1
+  for (const digit of reversedStringOneChars) {
+    const digitNumber = baseOneCharacters.indexOf(digit)
+    if (digitNumber === -1) {
+      throw new TypeError(`Not a valid character: ${digit}`)
+    }
+    value += (digitNumber * placeValue)
+    placeValue *= stringOneBase
+  }
+  let stringInBaseTwo = ''
+  const stringTwoBase = baseTwoCharacters.length
+  while (value > 0) {
+    const remainder = value % stringTwoBase
+    stringInBaseTwo = baseTwoCharacters.charAt(remainder) + stringInBaseTwo
+    value /= stringTwoBase
+  }
+  const baseTwoZero = baseTwoCharacters.charAt(0)
+  return stringInBaseTwo.replace(new RegExp(`^${baseTwoZero}+`), '')
+}
+
+(() => {
+  console.log(convertArbitraryBase('98', '0123456789', '01234567'))
+  console.log(convertArbitraryBase('98', '0123456789', 'abcdefgh'))
+  console.log(convertArbitraryBase('129', '0123456789', '01234567'))
+})()