javascript 光滑的滚动顶部

Posted 2021-05-03

function scrollToSmoothly(pos, time) {
         if (typeof pos !== 'number') {
            pos = parseFloat(pos);
         }
         if (isNaN(pos)) {
            console.warn('Position must be a number or a numeric String.');
            throw 'Position must be a number';
         }
         if (pos < 0 || time < 0) {
            return;
         }
         let currentPos = window.scrollY || window.screenTop;
         let start = null;
         time = time || 500;
         window.requestAnimationFrame(function step(currentTime) {
            start = !start ? currentTime : start;
            if (currentPos < pos) {
               let progress = currentTime - start;
               window.scrollTo(
                  0,
                  ((pos - currentPos) * progress) / time + currentPos
               );
               if (progress < time) {
                  window.requestAnimationFrame(step);
               } else {
                  window.scrollTo(0, pos);
               }
            } else {
               let progress = currentTime - start;
               window.scrollTo(
                  0,
                  currentPos - ((currentPos - pos) * progress) / time
               );
               if (progress < time) {
                  window.requestAnimationFrame(step);
               } else {
                  window.scrollTo(0, pos);
               }
            }
         });
      }