Détecte si un élément entre ou sort du viewport pour lui ajouter ou enlever une class CSS

onViewport.js

(function($) {

  /**
   * Copyright 2012, Digital Fusion
   * Licensed under the MIT license.
   * http://teamdf.com/jquery-plugins/license/
   *
   * @author Sam Sehnert
   * @desc A small plugin that checks whether elements are within
   *     the user visible viewport of a web browser.
   *     only accounts for vertical position, not horizontal.
   */

  $.fn.visible = function(partial) {
    
      var $t            = $(this),
          $w            = $(window),
          viewTop       = $w.scrollTop(),
          viewBottom    = viewTop + $w.height(),
          _top          = $t.offset().top,
          _bottom       = _top + $t.height(),
          compareTop    = partial === true ? _bottom : _top,
          compareBottom = partial === true ? _top : _bottom;
    
    return ((compareBottom <= viewBottom) && (compareTop >= viewTop));

  };
    
})(jQuery);


function onViewport( element, className ){
  $( element ).each(function(i, el) {
    var el = $(el);
    if (el.visible(true)) {
      el.addClass( className ); 
    } else {
      el.removeClass( className );
    }
  });

}

onViewport( ".svg-container", "animated" );

$(window).scroll(function(event) {
	onViewport( ".svg-container", "animated" );
});