¿what function do I use to add a new item?

[wuyuedefeng]

you can add a item into tree data. eg: your data is below

 treeData: {
        name: 'root',
        children: [
          {
            name: '2',
            children: [
              { name: '2-1' }
            ]
          }
      ]     
}

push your item to children which you want add!