How to detect mousein and mouseleave in pure JavaScript?
<p>I can't use jQuery for this part of the project due to various reasons. SO I need to detect this in vanilla js. I tried this but it doesn't work:</p>

<p><a href="http://jsfiddle.net/qHfJD/" rel="nofollow">http://jsfiddle.net/qHfJD/</a></p>

<pre><code>var myDiv = document.getElementById('foo');

myDiv.onmouseenter = function() { 
    alert('entered');
}

myDiv.onmouseleave = function() { 
    alert('left');
}
</code></pre>
