Fx on JavaScript: How to fade stuff, etc without frameworks?

I would like to learn how to do fade, and similar effects on JavaScript. I often get answers, like why not use jQuery, Mootools, etc ? Well, I want to learn how stuff works, then I won't mind using any of these frameworks.

I'm currently learning about making changes on the DOM, so, I've read a lot of stuff on this theme. Also, I've read about Reflow, still, I didn't find any cool stuff on Repaint, but, I'll keep searching.

From seeing source files etc, I see a few methods, that I don't know if they've created or are Core methods of JS.

My question is, is there any resource where I can learn all this neat stuff like smooth position change, fading elements trough opacity or whatever, etc?

here's an example that works in firefox and chrome. ie doesn't respect the opacity style.

    var ELEMENT;
    var STEPS;
    var INTERVAL;
    var COUNT;
    var TIMERID;

    // 5 * 200ms = 1 second
    STEPS = 5;
    INTERVAL = 200;

    function Button1_onclick() {

        ELEMENT = document.getElementById("foo");
        COUNT = STEPS - 1;
        TIMERID = setInterval(Fade, INTERVAL);
    }

    function Fade() {

        ELEMENT.style.opacity = String(COUNT / STEPS);
        COUNT--;

        if (COUNT < 0) {
            clearInterval(TIMERID);
            TIMERID = 0;
        }
    }

setInterval and clearInterval are standard js functions. they will execute the given function every x milliseconds. in our case we kill it when we've hit 0 opacity.

sliding a window is a similar process. you'd set the left/right/top/bottom style instead of opacity.