Javascript has not class, it has only function. So its inheritance is somewhat confusing. Before we talk about inheritance, let's make sure we understanding the basic. Here is the fact.
        <ol>
        <li>a function has property "prototype", the prototype object's points back to the function itself.
        <img src="http://msdn.microsoft.com/msdnmag/issues/07/05/JavaScript/fig03.gif" />

        <p>beforeunload happend before unload. beforeunload can give user a message, asking user if want to contine or not, if yes, unload event will trigger and unload can show user a message, but can not block to unload the page. Below is the sample.</p>

        <h4>Slide In</h4>
        <p>A Function for Slowly Revealing a Hidden Element by Increasing Its Height Over a
        Matter of One Second.</p>

        <p>
        In CSS, elements are positioned using
        offsets. The measurement used is the amount of offset from the top-left corner of an element’s parent.
        </p>

        <pre data-sub="prettyprint:_">
        // Get a style property (name) of a specific element (elem)
        function getStyle( elem, name )
        {
        // If the property exists in style[], then it's been set
        // recently (and is current)
        if (elem.style[name])
        {
        return elem.style[name];
        }
        // Otherwise, try to use IE's method
        else if (elem.currentStyle)
        {
        return elem.currentStyle[name];
        }
        // Or the W3C's method, if it exists
        else if (document.defaultView && document.defaultView.getComputedStyle)
        {
        // It uses the traditional 'text-align' style of rule writing,
        // instead of textAlign
        name = name.replace(/([A-Z])/g,"-$1");
        name = name.toLowerCase();
        // Get the style object and get the value of the property (if it exists)
        var s = document.defaultView.getComputedStyle(elem,"");
        return s && s.getPropertyValue(name);
        // Otherwise, we're using some other browser
        } else
        return null;
        }
        </pre>