Merge branch 'master' into fix-issue#14

src/Tree.js

@@ -1,5 +1,3 @@
-let nodeId = 1
-
 /**
  * Tree data struct
  * Created by ayou on 2017/7/20.
@@ -13,7 +11,7 @@ let nodeId = 1
 const TreeNode = function (data) {
   const { id, isLeaf } = data
   // this.name = name
-  this.id = (typeof id === 'undefined') ? ('new' + nodeId++) : id
+  this.id = (typeof id === 'undefined') ? new Date().valueOf() : id
   this.parent = null
   // this.pid = null
   this.children = null

src/VueTreeList.vue

@@ -69,10 +69,11 @@
         @dragleave="dragLeaveBottom"></div>
     </div>
 
-    <div :class="{'vtl-tree-margin': model.name !== 'root'}" v-show="expanded" v-if="isFolder">
+    <div :class="{'vtl-tree-margin': model.name !== 'root'}" v-show="model.name === 'root' || expanded" v-if="isFolder">
       <item v-for="model in model.children"
         :default-tree-node-name="defaultTreeNodeName"
         :default-leaf-node-name="defaultLeafNodeName"
+        v-bind:default-expanded="defaultExpanded"
         :model="model"
         :key='model.id'>
       </item>
@@ -94,7 +95,7 @@
         isDragEnterUp: false,
         isDragEnterBottom: false,
         isDragEnterNode: false,
-        expanded: true
+        expanded: this.defaultExpanded
       }
     },
     props: {
@@ -111,7 +112,11 @@
       },
       onDeleteNode: {
         type: Function,
-        default: (confirm) => {confirm()}
+        default: (confirm) => {confirm()
+      },
+      defaultExpanded: {
+        type: Boolean,
+        default: true
       }
     },
     computed: {