how to create tree structure recursive json & query for it ,where id =5 in nodejs

Question

Table for my folder structure

 id |    name      | parent_id 
----+--------------+-----------
  1 | parent       |          
  2 | child        |         1
  3 | grandchild A |         2
  4 | grandchild B |         2
  5 | grandchild c |         3

select id,parent_id, name from table.

I want to create a json for this result set which should be in tree structure. how to make a json for this, please help.

Answer 1

Something like this?

{
  "1": {
      "name": "parent",
      "parent_id": 0
   },
  "2": {
     "name": "child",
     "parent_id": 1
  },
  "3": {
     "name": "grandchild a",
     "parent_id": 2
  }
}

Edit: Or array:

[
    { "id": 1, "name": "parent", "parent_id": 0},
    { "id": 2, "name": "child",  "parent_id": 1}
    // and so on
]

Answer 2

I guess I would structure the tree like this (with id's where appropriate):

{
     name: "parent"
     children: [
       {
          name: "child"
          children: [
             {
               name: "grandchild a"
              }   ,
             {
               name: "grandchild b"
              }   ,         
             {
               name: "grandchild c"
              }   
          ]   
        }
      ]
  }

What is your data structure inside of Node that you need to transform? If this is in a DB table, then how are you getting it into node and what does it look like once it is there - you could console.log(JSON.stringify(object, null 4)) to output the current structure

Answer 3

why dont yo do it like this:

function Directory(p_id, p_name){
  this.name = p_name;
  this.id = p_id;
  this.subdir = [];
}

Directory.prototype.addSubDir(p_directory){
  this.subdir.push(p_directory);
}

then somewhere in your code do this:

var arr_struc = ...;//[your data]
var dir_mem = [];
var rootDir = new Directory(0, 'ROOT')
dir_mem.push(rootDir);

for(var i = 0; i < arr_struc.length; i++){
  var tmp_directory = new Directory(i+1, arr_struc[i].name)
  dir_mem.push(tmp_directory);
  if(!arr_struc[i].parent_id)
    { rootDir.addSubDir(tmp_directory) }
  else
    { dir_mem[arr_struc[i].parent_id].addSubDir(tmp_directory) }
}

adding some other methods to read subdirectorys by ID or simular and returning "this" you would be able to get subdirectorys by methodchaining ;) pretty OO style but I think its a nice way to structure code

Hope it helped in your special case

EDIT: here is an example of methodchaining your subdir's:

Directory.prototype.getSubDirs(){
  return this.subDir;
}
Directory.prototype.getSubDirById(p_id){
  var allSubDirs = this.getSubDirs();
  for(var i = 0; i < allSubDirs.length; i++){
    if(allSubDirs[i].id === p_id) return allSubDirs[i];
  }
  return false;
}
Directory.prototype.getSubDirByName(p_name){
  var allSubDirs = this.getSubDirs();
  for(var i = 0; i < allSubDirs.length; i++){
    if(allSubDirs[i].name === p_name) return allSubDirs[i];
  }
  return false;
}

Then you could do:

rootDir.getSubDirByName('parent').getSubDirByName('child').getSubDirByName('grandchild A');

or something like that :) -crazy

Answer 4

On a project I worked on for the Rwandan NGO Solid Africa, tree structure was a important part of keeping track of expenses and donations (your expense or donation belonged to a category, food, special care etc.). Based on this experience I developed the tree-util node package.

To get a tree structure including some handy methods do this:

1. Install the package with this command: npm install tree-util

2. You need to get the data represented as json. If it is a table in the database, a simple select using a node package will get you the data as json.

3. Build the tree based on the json data loaded from the db. A more generic example can be below, but it can be adjusted by changing the items array to be the data loaded from your table and setting the parentid property of the config to be 'parent_id'

var tree_util = require('tree-util')
 
// An array where the items has a parent child reference using id properties 
var items = [{ id : 1 }, { id : 2, parentid : 1 }, { id : 3, parentid : 1 },
             { id : 4, parentid : 1 }, { id : 5, parentid : 3 }];
 
// Config object to set the id properties for the parent child relation 
var standardConfig =  { id : 'id', parentid : 'parentid'};
 
// Creates an array of trees. For this example there will by only one tree 
var trees = tree_util.buildTrees(items, standardConfig);