[Improvement] Tab animation fluency && position (#379)

packages/utils/raf.js

@@ -0,0 +1,32 @@
+/**
+ * requestAnimationFrame polyfill
+ */
+
+import { isServer } from './index';
+
+let prev = Date.now();
+function fallback(fn) {
+  const curr = Date.now();
+  const ms = Math.max(0, 16 - (curr - prev));
+  const id = setTimeout(fn, ms);
+  prev = curr + ms;
+  return id;
+}
+
+const global = isServer ? global : window;
+const iRaf =
+  global.requestAnimationFrame ||
+  global.webkitRequestAnimationFrame ||
+  fallback;
+const iCancel =
+  global.cancelAnimationFrame ||
+  global.webkitCancelAnimationFrame ||
+  global.clearTimeout;
+
+export function raf(fn) {
+  return iRaf.call(global, fn);
+}
+
+export function cancel(id) {
+  iCancel.call(global, id);
+}