yuanchuan/gist:833201

## gistfile1.html
<!doctype html>
<html>
<head>
  <meta charset="utf-8" />
  <title> An interesting question</title>
  <style>
    table {
      border-collapse:collapse;
      border-spacing:0;
      margin: 100px auto 0;
    }
    p, td {
      text-align:center;
    }
    td {
      padding: 0 5px;
      width:100px;
      height:100px;
      line-height:100px;
      border:1px solid #bbb;
      font-size:2em;
      color:red;
    }
    #button {
      padding: 15px 136px;
      cursor:pointer;
      font-weight:bold;
      color:blue;
    }
  </style>

  <script>

    var Ring = (function() {
      function Ring(list) {
        this._list = [].slice.call(list, 0);
        this._length = this._list.length;
        this._curr = -1;
      };
      Ring.prototype = {
        rollTo: function(idx) {
          this._curr = idx % this._length;
          if (this._curr < 0) this._curr += this._length;
          return this._list[this._curr];
        },
        next: function() {
          return this.rollTo(this._curr + 1);
        },
        prev: function() {
          return this.rollTo(this._curr - 1);
        }
      };
      return function(list) {
        return new Ring(list);
      };
    }());

    window.onload = function() {
      var numClicked = 0
        , cells = Ring(
           document.getElementsByTagName('td')
          );

      document.getElementById('button')
        .onclick = function() {
          cells.next().innerHTML = (++numClicked);
        }
    }

  </script>
</head>

<body>
  <table>
    <tbody>
      <tr><td></td><td></td><td></td></tr>
      <tr><td></td><td></td><td></td></tr>
      <tr><td></td><td></td><td></td></tr>
    </tbody>
  </table>
  <p><input id="button" type="button" value="Click me!"/></p>
</body>
</html>
	<!doctype html>
	<html>
	<head>
	<meta charset="utf-8" />
	<title> An interesting question</title>
	<style>
	table {
	border-collapse:collapse;
	border-spacing:0;
	margin: 100px auto 0;
	}
	p, td {
	text-align:center;
	}
	td {
	padding: 0 5px;
	width:100px;
	height:100px;
	line-height:100px;
	border:1px solid #bbb;
	font-size:2em;
	color:red;
	}
	#button {
	padding: 15px 136px;
	cursor:pointer;
	font-weight:bold;
	color:blue;
	}
	</style>

	<script>

	var Ring = (function() {
	function Ring(list) {
	this._list = [].slice.call(list, 0);
	this._length = this._list.length;
	this._curr = -1;
	};
	Ring.prototype = {
	rollTo: function(idx) {
	this._curr = idx % this._length;
	if (this._curr < 0) this._curr += this._length;
	return this._list[this._curr];
	},
	next: function() {
	return this.rollTo(this._curr + 1);
	},
	prev: function() {
	return this.rollTo(this._curr - 1);
	}
	};
	return function(list) {
	return new Ring(list);
	};
	}());

	window.onload = function() {
	var numClicked = 0
	, cells = Ring(
	document.getElementsByTagName('td')
	);

	document.getElementById('button')
	.onclick = function() {
	cells.next().innerHTML = (++numClicked);
	}
	}

	</script>
	</head>

	<body>
	<table>
	<tbody>
	<tr><td></td><td></td><td></td></tr>
	<tr><td></td><td></td><td></td></tr>
	<tr><td></td><td></td><td></td></tr>
	</tbody>
	</table>
	<p><input id="button" type="button" value="Click me!"/></p>
	</body>
	</html>