How can I detect scroll end of the specified element by JavaScript?

Question

I'm using Google Chrome 10 and writing JavaScript to detect scroll end.

To detect scroll end of window , the code below worked fine:

window.addEventListener(
    'scroll',
    function()
    {
        var scrollTop = document.documentElement.scrollTop ||
            document.body.scrollTop;
        var offerHeight = document.body.offsetHeight;
        var clientHeight = document.documentElement.clientHeight;
        if (offsetHeight <= scrollTop + clientHeight)
        {
            // Scroll end detected
        }
    },
    false
);

Now I want to detect scroll end of the specified element, like <section id="box" style="height: 500px; overflow: auto;">
This is the code that doesn't detect correctly:

document.getElementById('box').addEventListener(
    'scroll',
    function()
    {
        var scrollTop = document.getElementById('box').scrollTop;
        var offerHeight = document.getElementById('box').offsetHeight;
        var clientHeight = document.getElementById('box').clientHeight;
        if (offsetHeight <= scrollTop + clientHeight)
        {
            // This is called before scroll end!
        }
    },
    false
);

Could someone please fix my code? Thanks.

Answer 1

Fixed.

document.getElementById('box').addEventListener(
    'scroll',
    function()
    {
        var scrollTop = document.getElementById('box').scrollTop;
        var scrollHeight = document.getElementById('box').scrollHeight; // added
        var offsetHeight = document.getElementById('box').offsetHeight;
        // var clientHeight = document.getElementById('box').clientHeight;
        var contentHeight = scrollHeight - offsetHeight; // added
        if (contentHeight <= scrollTop) // modified
        {
            // Now this is called when scroll end!
        }
    },
    false
)