Simple minimal version of https://github.com/mrloop/vehicle-app, run via node `node part.js`

part.js

var part = function (spec) {
  var that = {
    getName: function (){
      return spec.name
    },

    toString: function () {
      var str = this.getName() + '\n' + this.getCents() + '\n';
      return str + this.map(spec.parts, function(part){
        return part.toString();
      }).join('');
    },

    setParts: function(parts) {
      spec.parts = parts;
    },

    getParts: function () {
      return spec.parts;
    },

    getCents: function() {
      return spec.cents || 0;
    },

    findPartsWithFnc: function (fnc) {
      var arr = [];
      if(fnc(this)){
        arr = [this];
      }
      return this.reduce(spec.parts, function(array, part){
        return array.concat(part.findPartsWithFnc(fnc));
      }, arr);
    },

    reduceWithFnc: function (fnc){
      var val = fnc(this);
      return this.reduce(spec.parts, function(sum, part){
        return sum + part.reduceWithFnc(fnc);
      }, val);
    },

    findPartsWithName: function(name){
      return this.findPartsWithFnc(function (part){
        return part.getName() === 'engine';
      });
    },

    findPartWithName: function(name){
      return this.findPartsWithName(name)[0];
    },

    getTotalCost: function(){
      return this.reduceWithFnc(function(part){
        return part.getCents();
      });
    },

    reduce: function (array, fnc, mem) {
      if(isArray(array)){
        for(var i=0; i< array.length; i++) {
          mem = fnc(mem, array[i]);
        }
      }
      return mem;
    },

    map: function (array, fnc) {
      var arr = [];
      if(isArray(array)){
        for(var i=0; i< array.length; i++) {
          arr.push(fnc(array[i]));
        }
      }
      return arr;
    }
  };
  return that;
};


var json = {
  name: 'car',
  cents: 123123,
  parts: [
    {
      name: 'engine',
      parts: [{
          name: 'piston',
          cents: 1233
        },{
          name: 'piston',
          cents: 1443
        },
        {
          name: 'bolt',
          cents: 17
        },{
          name: 'bolt',
          cents: 17
        }]
    },{
      name: 'wheels',
      parts: [{
        name: 'wheel',
        cents: 1200,
        parts: [{
          name: 'bolt',
          cents: 15
        },{
          name: 'bolt',
          cents: 15
        },{
          name: 'bolt',
          cents: 15
        }]
      },{
        name: 'wheel',
        cents: 1200,
        parts: [{
          name: 'bolt',
          cents: 15
        },{
          name: 'bolt',
          cents: 15
        },{
          name: 'bolt',
          cents: 15
        }]
      }]
    },{
      name: 'body',
      cents: 456,
      parts: [{
        name: 'bolt',
        cents: 13
      },{
        name: 'bolt',
        cents: 13
      }]
    }
  ]

}

var buildFromParts = function (json) {
  if(isArray(json)){
    var arr = []
    for(var i=0; i<json.length; i++){
      arr.push(buildFromParts(json[i]));
    }
    return arr;
  }else{
    var parts = json.parts;
    delete(json, 'parts');
    var p = part(json);
    if(parts){
      p.setParts(buildFromParts(parts));
    }
    return p;
  }
}

var isArray = function (thing) {
  return Object.prototype.toString.call(thing) === '[object Array]';
}

var car = buildFromParts(json);
console.log(car.toString());
console.log(car.findPartWithName('engine').getName());
console.log(car.getTotalCost());