A simple lazyload plugin for Zepto/jQuery

Zepto.lazyload.js

(function($){
  $.fn.lazyload = function(options){
    var $container = options.$container,
      $window = $(window),
      elems = [];

    options = $.extend({
      attr: 'data-lazyload',
      $container: $window,
      advance: 100,
      placeholder: 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mNgYAAAAAMAASsJTYQAAAAASUVORK5CYII=',
      callback: function(){}
    },options);

    $(this).find( '[' + options.attr + ']').each(function(i,elem){
      var $self = $(this);
      $self.attr('src',options.placeholder);
      elems.push({
        $elem : $self,
        tag : this.nodeName.toLowerCase(),
        top : $self.offset().top - options.advance,
        url : $self.attr(options.attr)
      });
    });

    var handler = function(callback){
      var h = $container.height(),
        top,
        i, l, cur, $o;
      if ( $container[0] === $container[0].window ) {
        top = $window.scrollTop();
      } else {
        top = $container.offset().top;
      }

      for( i = 0 , l = elems.length; i < l ; i++ ){
        cur = elems[i];
        $o = cur.$elem;
        if( cur.top < h + top ){
          if( cur.url ){
            if (cur.tag === "img") {
              $o.attr("src", cur.url);    
            } else {
              $o.load(url, {}, function(){});
            }
            $o.attr(options.attr,null);
          }
          elems.splice(i,1);
          i--;
          l--;
          $.isFunction(callback) && callback($o);
        }
      }
    };

    handler(options.callback);
    $container.on('scroll',handler);
    $window.on('resize',handler);
  };
})(Zepto);