Convert flat data to hierarchical with inner objects javascript -

i faced common issue converting simple flat data hierarchical. have found multiple topics still can't how convert flat data necessary me hierarchical format

this json

    [   {     "id": 1,     "name": "sponsor",     "description": null,     "parentid": null   },   {     "id": 2,     "name": "class",     "description": null,     "parentid": 1   },   {     "id": 3,     "name": "study",     "description": null,     "parentid": 2   },   {     "id": 4,     "name": "site",     "description": null,     "parentid": 3   } ] 

and need format this

  [     {       "data":{         "id": 1,         "name":"sponsor",         "description":null,         "parentid":"null"       },       "children":[         {           "data":{             "id": 2,             "name":"class",             "description":null,             "parentid":"1"           },           "children":[             {               "data":{                 "id": 3,                 "name":"study",                 "description":null,                 "parentid":"2"               },              "children": [                 {                    "data":{                       "id": 4,                      "name":"site",                      "description":null,                      "parentid":"3"                    }                  }               ]             }           ]         }       ]     }   ] 

this function

    flattohierarchy(flat) {      let roots = [];     let = {};      flat.foreach(function (item) {       all[item.id] = item     });      object.keys(all).foreach(function (id) {       let item = all[id];       if (item.parentid === null) {         roots.push(item)       } else if (item.parentid in all) {         let p = all[item.parentid];         if (!('children' in p)) {           p.children = []         }         p.children.push(item)       }     });      console.log(roots);     return roots   } 

output

    [   {     "id": 1,     "name": "sponsor",     "description": null,     "parentid": null,     "children": [       {         "id": 2,         "name": "class",         "description": "together",         "parentid": 1,         "children": [           {             "id": 3,             "name": "study",             "description": "browsing data",             "parentid": 2,             "children": [               {                 "id": 4,                 "name": "site",                 "description": null,                 "parentid": 3,                 "children": []               }             ]           }         ]       }     ]   }   ] 

i'm pretty close desire result. me fix ?

edited

the right answer provided @someone3 modified code needs

    flattohierarchy (flat) {      let roots = [];     let = {};     let ids = [];      flat.foreach(function (item) {       let itemid = item.id;       let converteditem = function (id) {         let newitem = {};         newitem['data'] = id;         return newitem;       } ;       all[itemid] = converteditem(item);       ids.push(itemid);     });      (let = 0; < ids.length; i++) {       let id = ids[i];       let converteditem = all[id];       let parentid = converteditem.data.parentid;        if (parentid === null) {         roots.push(converteditem);       } else if (parentid in all) {         let p = all[parentid];         if (!('children' in p)) {           p.children = []         }         p.children.push(converteditem)       }     }     return roots   } 

the code below full source code situation. modified , added few lines source code. note code assumes parents inserted tree before children do. if assumption not true code need changed more this.

let flatdata = [   {     "id": 1,     "name": "sponsor",     "description": null,     "parentid": null   },   {     "id": 2,     "name": "class",     "description": null,     "parentid": 1   },   {     "id": 3,     "name": "study",     "description": null,     "parentid": 2   },   {     "id": 4,     "name": "site",     "description": null,     "parentid": 3   } ];  function convertitem(item) {   let newitem = {};   newitem.data = item;     return newitem; }  function flattohierarchy(flat) {      let roots = [];     let = {};     let ids = [];      flat.foreach(function (item) {       let itemid = item.id;       let converteditem = convertitem(item);       all[itemid] = converteditem;       ids.push(itemid);     });      // use ids array instead of object maintain previous order.     (let = 0; < ids.length; i++) {       let id = ids[i];       let converteditem = all[id];       let parentid = converteditem.data.parentid;        if (parentid === null) {         delete converteditem.data.parentid;         delete converteditem.data.id;         roots.push(converteditem);       } else if (parentid in all) {         let p = all[parentid];         if (!('children' in p)) {           p.children = []         }         delete converteditem.data.parentid;         delete converteditem.data.id;         p.children.push(converteditem)       }     };      console.log(roots);     return roots   }    flattohierarchy(flatdata); 

we can factor out 2 deletes before push.