## Function(treeId, treeNode)setting.callback.beforeAsync

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

Used to capture the event before zTree execute ajax, zTree based on return value to determine whether to execute ajax.

Default: null

### Function Parameter Descriptions

#### treeIdString

zTree unique identifier: treeId, easy for users to control.

#### treeNodeJSON

JSON data object of the parent node

When asynchronously loading the root, the treeNode = null

#### Return Boolean

return true or false

If return false, zTree will not execute ajax, and will not trigger the 'onAsyncSuccess / onAsyncError' callback.

### Examples of setting & function

#### 1. If the parent node's attribute 'id' is 1, zTree will not execute ajax.

    function zTreeBeforeAsync(treeId, treeNode) {
        return (treeNode.id !== 1);
    };
    var setting = {
    	callback: {
    		beforeAsync: zTreeBeforeAsync
    	}
    };
    ......