prevent multiple button pressing
<p>I have a simple countdown that is activated by a button. Using <code>onclick</code> i start the action, but I noticed that if you keep pressing the button it increases the time and the countdown is out of sync. How would I go about preventing this from happening, and only allowing one click at a time?</p>

<pre><code>  var count = 10,
      startcounter = document.getElementById("stercount");

startcounter.onclick = function() {
  countdown = setInterval(function(){
    document.getElementById("countdown").innerHTML = count + " seconds remaining!";
    if (count &lt;= 0) {
      clearInterval(countdown);
      document.getElementById("countdown").innerHTML = "Done!";
    }
    count--;
  }, 1000);
};
</code></pre>

<p>DEMO: <a href="http://jsfiddle.net/StWXk/1/" rel="nofollow">http://jsfiddle.net/StWXk/1/</a>
​</p>
