add loading

src/loading.js

@@ -0,0 +1,25 @@
+import Icons from './icons';
+
+export default class Loading {
+  constructor(art) {
+    this.art = art;
+    this.init();
+  }
+
+  init() {
+    const { option } = this.art;
+    if (option.loading) {
+      this.art.refs.$loading.insertAdjacentHTML('beforeend', option.loading);
+    } else {
+      this.art.refs.$loading.appendChild(Icons.loading);
+    }
+  }
+
+  hide() {
+    this.art.refs.$loading.style.display = 'none';
+  }
+
+  show() {
+    this.art.refs.$loading.style.display = 'block';
+  }
+}