Javascript Hashcash tests using CryptoJS

hashcash.html

<form id="feedback">
	Username: <input name="username">

	<input type="hidden" class="nounce" value="foobar">
	<input type="hidden" class="time" value="123456789">
</form>

<script src="http://crypto-js.googlecode.com/svn/tags/3.1.2/build/rollups/sha256.js"></script>
<script>
	
	function sha256(string) {
		return CryptoJS.SHA256(string).toString(CryptoJS.enc.Hex);
	}

	function Hashcash(text, zeroes) {
		var count = 0;
		var pad = '0000000000000000000'.substring(0, zeroes);

		return function(iterations) {

			while(iterations > 0) {
				var hash = sha256(text + count);
				if(pad == hash.substring(0, zeroes)) {
					return count;
				}
				count++;
				iterations--;
			}
			
			return false;
		};
	}
	
	// Thanks to Mike Ash for his HashcashBG/setTimeout idea
	function HashcashBG(text, zeroes, callback) {
		var iterations = 100;
		var delay = 1;
		var processor = Hashcash(text, zeroes);

		var f = function() {

			var count = processor(iterations);

			if(count) {
				callback(count);
				return;
			}

			setTimeout(f, delay);
		};

		f();
	}


	function HashcashForm(form, nounce)
	{
		var nounce = form.getElementsByClassName(nounce);

		// We only care about forms with a nounce to hash
		if(nounce.length) {

			HashcashBG(nounce[0].value, 3, function(count) {

				console.log(sha256(nounce[0].value + count), count);

				var input = document.createElement("input");
				input.value = count;
				input.className = "hashcash";
				input.type = "hidden";

				console.log(input);

				form.appendChild(input);
			});

		}
	}


	// On page load, or AJAX request complete
	//HashcashForm();

	var forms = document.getElementsByTagName('form');

	for (i = 0; i < forms.length; ++i) {
		HashcashForm(forms[i], 'nounce');
	}


</script>