html - How do you make something to appear slowly on a page using Javascript?

Question

Is there easier way to make something to appear slowly on webpage? I tried to incrementally increase opacity of the CSS, but it (opacity) tag is different for each browser. Is there well know Javascript function that everyone uses? Or is there any css tag?

[edit] Thanks for Jquery suggestion. Is there other option? My page is very small and don't want to add Jquery. (I know about Google hosting it)

Answer 1

Aargh! Every JS developer here seems to have contracted the jqueryitis!
If you're not yet infected or still want to escape from it, here's a small function that do the job cross browser :)

function appear(elm, i, step, speed){
    var t_o;
    //initial opacity
    i = i || 0;
    //opacity increment
    step = step || 5;
    //time waited between two opacity increments in msec
    speed = speed || 50; 

    t_o = setInterval(function(){
        //get opacity in decimals
        var opacity = i / 100;
        //set the next opacity step
        i = i + step; 
        if(opacity > 1 || opacity < 0){
            clearInterval(t_o);
            //if 1-opaque or 0-transparent, stop
            return; 
        }
        //modern browsers
        elm.style.opacity = opacity;
        //older IE
        elm.style.filter = 'alpha(opacity=' + opacity*100 + ')';
    }, speed);
}

To appear

appear(document.getElementsByTagName('DIV')[0], 0, 5, 40);

To disappear

appear(document.getElementsByTagName('DIV')[0], 100, -5, 40);