Restore demo

src/views/dropdown/DropdownDemo.vue

@@ -47,15 +47,15 @@ import DropdownDoc from './DropdownDoc';
 export default {
     data() {
         return {
-            selectedCity1: 0,
+            selectedCity1: null,
             selectedCity2: null,
             selectedCountry: null,
             cities: [
-                {name: 'New York', code: 1},
-                {name: 'Rome', code: 2},
-                {name: 'London', code: 0},
-                {name: 'Istanbul', code: 4},
-                {name: 'Paris', code: 5}
+                {name: 'New York', code: 'NY'},
+                {name: 'Rome', code: 'RM'},
+                {name: 'London', code: 'LDN'},
+                {name: 'Istanbul', code: 'IST'},
+                {name: 'Paris', code: 'PRS'}
             ],
             countries: [
                 {name: 'Australia', code: 'AU'},