树结构中查找子孙节点方法

var objData = [
    {name:1,children:[
        name:1-1,children:[
               {name:1-1-1}
           ]
       ]},
    {name:2,children:[
        name:2-1,children:[
               {name:2-1-1}
           ]
      ]},       
    {name:3,}
]

function sonsTree(arr,id){
    var temp = [],lev=0;
    var forFn = function(arr, id, lev){
        for (var i = 0; i < arr.length; i++) {
            var item = arr[i];
            let idd = item.parent_id?item.parent_id.toString():‘‘;
            if (idd == id) {
                item.lev=lev;
                temp.push(item);
                forFn(arr,item._id,lev+1);
            }
        }
    };
    forFn(arr, id,lev);
    return temp;
}