feat(hooks): add useRef hook

src/__tests__/useRef.test.ts

@@ -0,0 +1,45 @@
+import Vue from 'vue';
+import { computed, onMounted } from 'vue-function-api';
+import useRef from '../useRef';
+import renderHook from '../util/renderHook';
+
+describe('useRef', () => {
+  it('should be defined', () => {
+    expect(useRef).toBeDefined();
+  });
+
+  it('should return element when passing ref name', () => {
+    renderHook(() => {
+      const app = useRef<HTMLDivElement>('app');
+      const style = computed(() => (app.value ? app.value.style : undefined));
+
+      expect(app.value).toBeUndefined();
+      expect(style.value).toBeUndefined();
+
+      onMounted(async () => {
+        await Vue.nextTick();
+        expect(app.value).toBeDefined();
+        expect(style.value).toBeDefined();
+        expect(style.value.width).toBe('1280px');
+        expect(style.value.height).toBe('800px');
+      });
+    });
+  });
+
+  it('should return element when passing function', () => {
+    renderHook((_, { refs }) => {
+      const nav = useRef<HTMLDivElement>(() => refs.nav);
+      const style = computed(() => (nav.value ? nav.value.style : undefined));
+
+      expect(nav.value).toBeUndefined();
+      expect(style.value).toBeUndefined();
+
+      onMounted(async () => {
+        await Vue.nextTick();
+        expect(nav.value).toBeDefined();
+        expect(style.value).toBeDefined();
+        expect(style.value.width).toBe('100%');
+      });
+    });
+  });
+});

src/useRef.ts

@@ -0,0 +1,26 @@
+import Vue from 'vue';
+import { value, onMounted } from 'vue-function-api';
+import { getRuntimeVM } from './util/runtime';
+
+export type Ref = Vue | Element | Vue[] | Element[];
+
+export default function useRef<T extends Ref>(target: string | (() => Ref)) {
+  const ref = value<T>(undefined!);
+
+  onMounted(async () => {
+    await Vue.nextTick();
+    switch (typeof target) {
+      case 'string':
+        const { $refs } = getRuntimeVM(); // eslint-disable-line no-case-declarations
+        ref.value = $refs[target] as T;
+        break;
+      case 'function':
+        ref.value = target() as T;
+        break;
+      default:
+        throw new TypeError('Target must be string or function.');
+    }
+  });
+
+  return ref;
+}

src/util/renderHook.ts

@@ -24,8 +24,9 @@ export default function renderHook<V, Props = unknown>(
 ) {
   const App = createComponent({
     template: `
-      <div id="app">
-        <router-view></router-view>
+      <div ref="app" id="app" :style="{ width: '1280px', height: '800px' }">
+        <nav ref="nav" :style="{ width: '100%' }" />
+        <router-view />
       </div>
     `,