## Boolean / Function(treeId, treeNodes, targetNode)setting.edit.drag.prev

### Overview[ depends on jquery.ztree.exedit js ]

When drag one node to the target node, set whether to allow the node to be the target node's previous sibling. It is valid when [setting.edit.enable = true]

If the target node is root, so zTree will only trigger 'inner' and not trigger 'prev / next'.

This function mainly for the appropriate limit drag and drop (auxiliary arrow), it requires a combination of 'next, inner' together, to achieve full functionality.

Default: true

### Boolean Format

true means: allow the node to be the target node's previous sibling.

false means: don't allow the node to be the target node's previous sibling.

### Function Parameter Descriptions

#### treeIdString

zTree unique identifier: treeId.

#### treeNodesArray(JSON)

A collection of the nodes which has been dragged

#### targetNodeJSON

JSON data object of the target node which treeNodes are draged over.

#### Return Boolean

return true or false

### Examples of setting & function

#### 1. disable to drag the node to the target node's previous sibling.

    var setting = {
    	edit: {
    		enable: true,
    		drag: {
    			prev: false,
    			next: true,
    			inner: true
    		}
    	}
    };
    ......

#### 2. disable to drag the node to be all of the parent nodes's previous sibling.

    function canPrev(treeId, nodes, targetNode) {
    	return !targetNode.isParent;
    }
    var setting = {
    	edit: {
    		enable: true,
    		drag: {
    			prev: canPrev,
    			next: true,
    			inner: true
    		}
    	}
    };
    ......