js_tree_structure_to_nested_structure

 var first = d.filter(e=> !!!e.pId);
 var last = d.filter(e=> !!!e.id);
 
 
 var map = {};
 var idMap = {};
 
 d.forEach(d => {
 idMap[d.id] = d;
 if(map[d.pId]) {
 map[d.pId].push(d);
 }else{
 map[d.pId] = [d];
 }
 });
 console.log(JSON.parse(JSON.stringify(map)));
 for(var key in map) {
 if(idMap[key]) {
 // console.log("get children", key)
 idMap[key]['children'] = map[key];
 delete map[key];
 }
 }
 console.log(map);