初始化（包含登录模块）

wxcomponents/vant/mixins/observer/index.js

@@ -0,0 +1,19 @@
+import { behavior } from './behavior';
+export function observe(vantOptions, options) {
+    const { watch } = vantOptions;
+    options.behaviors.push(behavior);
+    if (watch) {
+        const props = options.properties || {};
+        Object.keys(watch).forEach(key => {
+            if (key in props) {
+                let prop = props[key];
+                if (prop === null || !('type' in prop)) {
+                    prop = { type: prop };
+                }
+                prop.observer = watch[key];
+                props[key] = prop;
+            }
+        });
+        options.properties = props;
+    }
+}