scrollend event futurfill.js

if (!('onscrollend' in document.documentElement)) {
  document.addEventListener('scroll',function(e){
    var scrollPort = e.target
    clearTimeout(scrollPort._scrollEndTimeout);
    scrollPort._scrollEndTimeout = setTimeout(function () {
      const event = new Event('scrollend');

      Object.defineProperty(event,'snapTarget',{
        get(){
          return 'todo';
        },
        set(){}
      })

      scrollPort.dispatchEvent(event);
    }, 100);
  },true);
}