base58: cleanup variable names

The encode/decode functions are also now similar syntactically.

src/base58.js

@@ -12,7 +12,7 @@ var ALPHABET = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'
 var ALPHABET_BUF = new Buffer(ALPHABET, 'ascii')
 var ALPHABET_MAP = {}
 for(var i = 0; i < ALPHABET.length; i++) {
-  ALPHABET_MAP[ALPHABET[i]] = BigInteger.valueOf(i)
+  ALPHABET_MAP[ALPHABET.charAt(i)] = BigInteger.valueOf(i)
 }
 var BASE = BigInteger.valueOf(58)
 
@@ -43,7 +43,7 @@ function encode(buffer) {
 function decode(string) {
   if (string.length === 0) return new Buffer(0)
 
-  var num = BigInteger.ZERO.clone()
+  var num = BigInteger.ZERO
 
   for (var i = 0; i < string.length; i++) {
     num = num.multiply(BASE)
@@ -55,16 +55,16 @@ function decode(string) {
   }
 
   // deal with leading zeros
-  var i = 0
-  while ((i < string.length) && (string[i] === ALPHABET[0])) {
-    i++
+  var j = 0
+  while ((j < string.length) && (string[j] === ALPHABET[0])) {
+    j++
   }
 
   var buffer = num.toBuffer()
-  var leadz = new Buffer(i)
-  leadz.fill(0)
+  var leadingZeros = new Buffer(j)
+  leadingZeros.fill(0)
 
-  return Buffer.concat([leadz, buffer])
+  return Buffer.concat([leadingZeros, buffer])
 }
 
 module.exports = {