Execute callbacks when element scrolls into view

executeWhenVisible.jquery.js

  $.fn.executeWhenVisible = function() {
    var _this = this;
    var callbacks = [].slice.call(arguments);
    var executed = false;

    $(window).on('scroll', function onScroll() {
      var relativeScroll = $(this).scrollTop() + $(this).height() - _this.offset().top;
      if (!executed && relativeScroll > 0) {
        executed = true;
        callbacks.forEach(function(callback) {
          if ($.isFunction(callback)) {
            callback.call(_this);
          }
        });
        $(window).off('scroll', onScroll);
      }
    });

    return this;
  };