refactor to vanilla js

src/base58.coffee

@@ -1,26 +0,0 @@
-class Base58Builder
-  constructor: ->
-    @alphabet = "123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ"
-    @base = @alphabet.length
-
-  encode: (num) ->
-    throw new Error('Value passed is not an integer.') unless /^\d+$/.test num
-    num = parseInt(num) unless typeof num == 'number'
-    str = ''
-    while num >= @base
-      mod = num % @base
-      str = @alphabet[mod] + str
-      num = (num - mod)/@base
-    @alphabet[num] + str
-
-  decode: (str) ->
-    num = 0
-    for char, index in str.split(//).reverse()
-      if (char_index = @alphabet.indexOf(char)) == -1
-        throw new Error('Value passed is not a valid Base58 string.')
-      num += char_index * Math.pow(@base, index)
-    num
-
-
-# Export module
-module.exports = new Base58Builder()

src/base58.js

@@ -0,0 +1,54 @@
+
+var alphabet = '123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ';
+var base = alphabet.length;
+
+// Create a lookup table to fetch character index
+var alphabetLookup = alphabet.split('').reduce(function (lookup, char, index) {
+	lookup[char] = index;
+	return lookup;
+}, {});
+
+function assertInteger(val) {
+	if (typeof val !== 'number' || isNaN(val) || Math.floor(val) !== val) {
+		throw new Error('Value passed is not an integer.');
+	}
+}
+
+function assertString(str) {
+	if (typeof str !== 'string') {
+		throw new Error('Value passed is not a string.');
+	}
+}
+
+function assertBase58Character(character) {
+	if (alphabetLookup[character] === undefined) {
+		throw new Error('Value passed is not a valid Base58 string.');
+	}
+}
+
+
+exports.encode = function (num) {
+	var str = '';
+	var modulus;
+
+	num = Number(num);
+
+	assertInteger(num);
+
+	while (num >= base) {
+		modulus = num % base;
+		str = alphabet[modulus] + str;
+		num = Math.floor(num / base);
+	}
+
+	return alphabet[num] + str;
+};
+
+exports.decode = function (str) {
+	assertString(str);
+
+	return str.split('').reverse().reduce(function (num, character, index) {
+		assertBase58Character(character);
+		return num + alphabetLookup[character] * Math.pow(base, index);
+	}, 0);
+};