Transform an object recursively in JavaScript

Question

I've been struggling with that problem for a few days. I have to transform an object into another object with a different structure.

from this:

{
  "a1" : "key",
  "a2" : {
    "b1" : "key",
    "b2" : {
      "c1" : "key"
    }
  }
}

to this:

{
  "key" : {
    "a1" : null,
    "a2" : [
      { 
        "b1" : null,
      },
      {
        "b2" : [
          "c1" : null
        ]
      }
    ]
  }
}

For better understanding, a1, a2, b1, b3 etc. would represent css selectors. null will be the value applied to the node. But for now, this shouldn't matter.

My current (non working) function looks like this:

var json = {};
var obj = {};

function build(objA){
  for(var a in objA){
    var key = objA[a]; 

    if(key instanceof Object){
      obj = {}; obj[a] = key;
      build(key);
    } else {
      json[key] = json[key] || {};

      if(obj == undefined){
        json[key][a] = null;
      } else {
        var p = firstKeyOf(obj);
        var key = obj[p][a];
        json[key][p] = json[key][p] || [];

        var selector = {};
        selector[a] = null;

        json[key][p].push(selector);
      }
    }
  }
}

which produces:

{
  "key" : {
    "a1" : null,
    "a2" : [
      {
        "b1" : null
      }
    ],
    "b2" : [
      {
        "c1" : null
      }
    ]
  }
}

What did i miss? I appreciate any help, thanks!

Well, for starters, your outermost object needs to be processed differently from any inner objects. — celticminstrel
– celticminstrel, Commented Jul 26, 2015 at 19:06
I think you'll need two functions, eg build() and buildsub(), where the former calls the latter, and the latter is recursive (calls itself). I'm guessing your current build() would then be fine except that the current recursive call would instead call buildsub(), but I'm not sure. — celticminstrel
– celticminstrel, Commented Jul 26, 2015 at 21:26
This is actually what i'm trying to implement now, a second recursive function. However, will see how it goes... — domizai
– domizai, Commented Jul 26, 2015 at 21:33

tkeram · Accepted Answer · 2015-07-26 21:37:20Z

1

Try this

var Converter = (function() {

var pic;

function _rec(a, o) {
    for(var k in o){
        var s = o[k];
        var arr = a.slice();
        arr.push(k);
        if (s instanceof Object) { _rec(arr, s); }
        else {
            if ("string" == typeof s) { arr.unshift(s); _attach(pic, arr); }
            else console.log('Invalid key type');
        }
    }
}

function _attach(p, m) {
    var k = m.shift(); 
    if ( ! p.hasOwnProperty(k)) p[k] = (m.length == 0) ? null : {};
    if (m.length > 0) p[k] = _attach(p[k], m);
    return p;
}

function _reverse(obj) { 
    if ( ! (obj instanceof Object)) console.log('First parameter need to be an Object'); 
    else { pic = {}; _rec([], obj); return pic; }
    }
return {
    reverse: _reverse,
    attach: _attach
}
})();

answered Jul 26, 2015 at 21:37

tkeram

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1 Comment

domizai Over a year ago

Hey! I tried it and it seems to do what i want. I will take a closer look tomorrow. thx!

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