Unveil() function from jQuery.unveil.js

unveil-func-jquery.js

function unveil() {
  // create an array of images that are in view
  // by filtering the intial array
  var inview = images.filter(function() {
    var $img = $(this);
    // if the image is hidden, don't bother
    if ($img.is(":hidden")) return;

    var wt = $w.scrollTop(), // window vertical scroll distance
        wb = wt + $w.height(), // last point of document visible in browser window
        et = $img.offset().top, // distance from document top to top of element
        eb = et + $img.height(); // distance from top of document to bottom of element

    // the bottom of the element is below the top of the browser (- threshold)
    // && the top of the element is above the bottom of the browser (+ threshold)
    return eb >= wt - th && et <= wb + th;
  });

  // trigger an 'unveil' event on each of the inview images
  inview.trigger("unveil");

  // filter the images to only those that aren't in view yet
  images = images.not(inview);
}