Question

I can’t get the actually LazyLoad plugin to work for me so I am trying to write my own with. Currently I have a list of images loading inside of a DIV. They are pulled by a PHP query to the mysql database. The DIV scroll is set to auto. The code I am using is:

<div id="b1" style="overflow:auto;">
<?PHP $result = mysql_query("SELECT * FROM images");

while($row = mysql_fetch_assoc($result)) {

echo "<img src='$row[photo]' style='display:none'> <br>";

}

</div>

<script type="text/javascript">
function imgCheck() {
var position        = $("img").offset().top;            
var scrollCheck       = $("#b1").scrollTop() + $("#b1").height();
if ( scrollCheck > position) {
  $("img").fadeIn("fast");
   }


$("#b1").scroll( function() { imgCheck() } );
</script>

Although this is not quite working for me. Could anyone help me out or shoot out some suggestions?

Answer 1

A couple of things:

• As the others have already said, your code has syntax errors – both with the PHP and the Javascript.
• If you use display: none, the elements will not take up any height, thus causing the entire thing to become unscrollable and fail.
• The first few elements should be visible without the user having to start scrolling

Taking these into consideration, we can try writing this this way:

// Cache the containing element and it's height
var b1 = $('#b1'),
    h = b1.height();

// Insert 20 img's - simulating server-side code
for(var i = 0; i < 20; i++){
    $('<img />', {
        src: 'http://placehold.it/100x100',
        alt: '',
        class: 'hidden',
        width: 100,
        height: 100
        // visibility: hidden to retain it's size
    }).css('visibility', 'hidden').appendTo(b1);
}

b1.scroll(function(){
    // Loop through only hidden images
    $('img.hidden').each(function(){
        // $(this).position().top calculates the offset to the parent
        // So scrolling is already taken care of here
        if(h > $(this).position().top){
            // Remove class, set visibility back to visible,
            // then hide and fade in image
            $(this).css('visibility', 'visible')
                .hide()
                .removeClass('hidden')
                .fadeIn(300);
        } else {
            // No need to check the rest - everything below this image
            // will always evaluate to false - so we exit out of the each loop
            return false;
        }
    });
    // Trigger once to show the first few images
}).trigger('scroll');

See a demo of this here: http://jsfiddle.net/yijiang/eXSXm/2