Make difficulty variable

Author: anders94

public/javascripts/blockchain.js

@@ -1,11 +1,29 @@
+var difficulty = 4;        // number of zeros required at front of hash
+var maximumNonce = 500000; // limit the nonce to this so we don't mine too long
+
+// NOTE: Because there are 16 possible characters in a hex value, each time you incrament
+// the difficulty by one you make the puzzle 16 times harder. In my testing, a difficulty
+// of 6 requires a maximumNonce well over 500,000,000.
+
+/////////////////////////
+// global variable setup
+/////////////////////////
+var pattern = '';
+for (var x=0; x<difficulty; x++) {
+  pattern += '0';
+}
+
+/////////////////////////
+// functions
+/////////////////////////
 function sha256(block, chain) {
   // calculate a SHA256 hash of the contents of the block
   return CryptoJS.SHA256(getText(block, chain));
 }
 
 function updateState(block, chain) {
   // set the well background red or green for this block
-  if ($('#block'+block+'chain'+chain+'hash').val().substr(0, 4) === '0000') {
+  if ($('#block'+block+'chain'+chain+'hash').val().substr(0, difficulty) === pattern) {
     $('#block'+block+'chain'+chain+'well').removeClass('well-error').addClass('well-success');
   }
   else {
@@ -30,10 +48,10 @@ function updateChain(block, chain) {
 }
 
 function mine(block, chain, isChain) {
-  for (var x = 0; x <= 500000; x++) {
+  for (var x = 0; x <= maximumNonce; x++) {
     $('#block'+block+'chain'+chain+'nonce').val(x);
     $('#block'+block+'chain'+chain+'hash').val(sha256(block, chain));
-    if ($('#block'+block+'chain'+chain+'hash').val().substr(0, 4) === '0000') {
+    if ($('#block'+block+'chain'+chain+'hash').val().substr(0, difficulty) === pattern) {
       if (isChain) {
         updateChain(block, chain);
       }