[improvement] add bind event mixin

packages/mixins/bind-event.js

@@ -0,0 +1,24 @@
+import { on, off } from '../utils/event';
+
+export function BindEventMixin(handler) {
+  function bind() {
+    if (!this.binded) {
+      handler.call(this, on);
+      this.binded = true;
+    }
+  }
+
+  function unbind() {
+    if (this.binded) {
+      handler.call(this, off);
+      this.binded = false;
+    }
+  }
+
+  return {
+    mounted: bind,
+    activated: bind,
+    destroyed: unbind,
+    deactivated: unbind
+  };
+}