unflatten an array of objects

unflatten.js

var _ = require("underscore")

var res = []

var arr = [
  {'id':21 ,'name' : 'name1' ,'vehiclename' : 'vehicle1' ,'parentid' : 21},
  {'id':21 ,'name' : 'name1' ,'vehiclename' : 'vehicle2' ,'parentid' : 21},
  {'id':22 ,'name' : 'name2' ,'vehiclename' : 'vehicle1' ,'parentid' : 22},
  {'id':22 ,'name' : 'name2' ,'vehiclename' : 'vehicle2' ,'parentid' : 22},
]

var connected = [{
  name: "vehicles",
  props: [ "vehiclename", "parentid" ]
}]

arr.forEach(function(e) {
  var obj = _.findWhere(res, { id: e.id })
  if(!obj) {
    obj = { id: e.id }
    res.push(obj)
  }
  var props = _.omit(e, "id");
  connected.forEach(function(cp) {
    props = _.omit.apply(this, [props, cp.props])
  })
  for(p in props) {
    copyPropToObj(props[p], p, obj);
  }
  connected.forEach(function(cp) {
    copyPropToObj(_.pick.apply(this, [e, cp.props]), cp.name, obj)
  })
})

function copyPropToObj(prop, propName, obj) {
  var oProp = _.clone(obj[propName])
  if(oProp && (prop === oProp)) {
    return
  } else if(oProp) {
    // we already have a value, need to move to an array
    obj[propName] = []
    obj[propName].push(prop)
    obj[propName].push(oProp)
  } else {
    // we don't have it set yet so just copy over
    obj[propName] = prop
  }
}

res.forEach(function(e) {
  console.log(e)
})