How to add smooth transitions to a very simple javascript slideshow

Question

I have the following JavaScript to make a slideshow:

window.addEventListener('load', main, false);

var number = 1;
var interval;

function main() {
    interval = setInterval(changeDia, 3000);
}

function changeDia() {
    var img = document.getElementById("dia");
    var currentDia = img.getAttribute("src");

    if(currentDia == "style/slideshow/6.jpg") {
        number = 1;
    } else {
        number = number + 1;
    }
    img.setAttribute("src", "style/slideshow/" + number + ".jpg");
}

This code works fine, but the transitions are very rude. I would like to have the current image to fade out and the next one to fade in so there's a smooth transition. What is the easiest way? Javascript and jQuery are both good for me.

Thanks in advance,

Cedric

Answer 1

You can do it easily using jQuery without plugins:

var i = 0,               //initial index
    duration = 1000,     //animation duration
    interval = 3000;     //interval

function switchImg() {
    $("<img>")                                               //create new <img>
        .attr("src", "style/slideshow/" + (i<6?++i:(i=1,i)) + ".jpg") //set attr.
        .css("opacity", 0)                                   //hide it
        .prependTo("#wrap")                                  //add it to DOM
        .animate({                                           //fade in
            opacity: 1
        }, {
            duration: duration
        })
        .next()                                              //select current img
        .animate({                                           //fade out
            opacity: 0
        }, {
            duration: duration
        })
        .promise()
        .done(function () {                                  //remove old img
            $(this).remove();                                // when done
            setTimeout(switchImg, interval);                 //repeat
        });
}
switchImg();                                                 //start up

http://jsfiddle.net/DerekL/vzhHZ/

Don't forget to set the position porperty of the images to absolute or else it won't work.