add raf util (#112)

* add raf util

* remove comment

* add test case

Author: yoyo837

src/raf.ts

@@ -0,0 +1,13 @@
+let raf = (fn: () => void) => +setTimeout(fn, 16);
+let caf = (num: number) => clearTimeout(num);
+
+if (typeof window !== 'undefined') {
+  raf = requestAnimationFrame;
+  caf = cancelAnimationFrame;
+}
+
+export default function wrapperRaf(callback: () => void): number {
+  return raf(callback);
+}
+
+wrapperRaf.cancel = caf;

tests/raf.test.js

@@ -0,0 +1,19 @@
+import raf from '../src/raf';
+
+describe('raf', () => {
+  it('test Raf', done => {
+    jest.useRealTimers();
+
+    let bamboo = false;
+    raf(() => {
+      bamboo = true;
+    });
+
+    expect(bamboo).toBe(false);
+
+    raf(() => {
+      expect(bamboo).toBe(true);
+      done();
+    });
+  });
+});