backTop.js

export default {
  bind(el, binding) {
    el.addEventListener('click', function () {
      var t = document.querySelector('.container-wrap').scrollTop
      var step=(t/100).toFixed(0);
      var timer=setInterval(function(){
        t=t-step;
        if(t<=0){
          t=0;
          clearInterval(timer);
        }
        document.querySelector('.container-wrap').scrollTop = t;
      },1)
    }, false);
  },
}