[improvement] rename packages dir to src (#3659)

src/utils/dom/raf.ts

@@ -0,0 +1,33 @@
+/**
+ * requestAnimationFrame polyfill
+ */
+
+import { isServer } from '..';
+
+let prev = Date.now();
+
+/* istanbul ignore next */
+function fallback(fn: FrameRequestCallback): number {
+  const curr = Date.now();
+  const ms = Math.max(0, 16 - (curr - prev));
+  const id = setTimeout(fn, ms);
+  prev = curr + ms;
+  return id;
+}
+
+/* istanbul ignore next */
+const root = <Window>(isServer ? global : window);
+
+/* istanbul ignore next */
+const iRaf = root.requestAnimationFrame || fallback;
+
+/* istanbul ignore next */
+const iCancel = root.cancelAnimationFrame || root.clearTimeout;
+
+export function raf(fn: FrameRequestCallback): number {
+  return iRaf.call(root, fn);
+}
+
+export function cancelRaf(id: number) {
+  iCancel.call(root, id);
+}