feat: migrate Sidebar component

src-next/sidebar/index.js

@@ -0,0 +1,40 @@
+import { createNamespace } from '../utils';
+import { ParentMixin } from '../mixins/relation';
+
+const [createComponent, bem] = createNamespace('sidebar');
+
+export default createComponent({
+  mixins: [ParentMixin('vanSidebar')],
+
+  props: {
+    modelValue: {
+      type: [Number, String],
+      default: 0,
+    },
+  },
+
+  data() {
+    return {
+      index: +this.modelValue,
+    };
+  },
+
+  watch: {
+    modelValue() {
+      this.setIndex(+this.modelValue);
+    },
+  },
+
+  methods: {
+    setIndex(index) {
+      if (index !== this.index) {
+        this.index = index;
+        this.$emit('change', index);
+      }
+    },
+  },
+
+  render() {
+    return <div class={bem()}>{this.$slots.default?.()}</div>;
+  },
+});