feat: scroll

Author: sl1673495

scroll.js

@@ -0,0 +1,48 @@
+export const raf = (() => {
+  return window.requestAnimationFrame ||
+    window.webkitRequestAnimationFrame ||
+    window.mozRequestAnimationFrame ||
+    window.oRequestAnimationFrame ||
+    window.msRequestAnimationFrame ||
+    function (callback) {
+      window.setTimeout(callback, 1000 / 60)
+    }
+})()
+
+let isScrolling = false
+let stop = false
+
+export function scroll (el, type, targetPos, time, next) {
+  if (isScrolling) {
+    stop = true
+  }
+  isScrolling = true
+  const start = Date.now()
+  const currentPos = el[type]
+
+  raf(step)
+
+  function step () {
+    const current = Date.now()
+    const rate = Math.min(1, (current - start) / time)
+    if (rate === 1) {
+      el[type] = targetPos
+      isScrolling = false
+      next && next()
+    } else {
+      el[type] = currentPos + (targetPos - currentPos) * rate
+      if (!stop) {
+        raf(step)
+      } else {
+        stop = false
+      }
+    }
+  }
+}
+
+document.addEventListener('visibilitychange', () => {
+  if (!document.hidden) {
+    isScrolling = false
+    stop = false
+  }
+})