Regrouping JSON object

Question

I wrote a JavaScript source which regrouping by new key i.e. following JSON to the other:

{
 "items" : [
 {
 "company" : "A"
 , "name" : "Prod_A01" 
 }
 , {
 "company" : "A"
 , "name" : "Prod_A02"
 }
 , {
 "company" : "B"
 , "name" : "Prod_B01"
 }
 ]
}

to:

{
 "A" : [
 {
 "company" : "A"
 , "name" : "Prod_A01" 
 }
 , {
 "company" : "A"
 , "name" : "Prod_A02"
 }
 ]
 , "B" : [
 {
 "company" : "B"
 , "name" : "Prod_B01"
 }
 ]
}

And here is logic:

function regroup(collection, key){
 var novo_obj = {};
 var type = typeof collection;
 var keyGroup = [];
 getKeyGroup(collection, key, keyGroup);
 for(var i = 0; i < keyGroup.length; i++) {
 novo_obj[keyGroup[i]] = [];
 gatherElements(collection, key, keyGroup[i], novo_obj[keyGroup[i]]);
 //console.log(novo_obj);
 }
 console.log(JSON.stringify(novo_obj));
 return novo_obj;
}
function gatherElements(collection, key, value, arr){
 //console.log(collection);
 if(typeof collection == 'object'){
 var targetValue = collection[key];
 if(typeof targetValue != 'undefined' && targetValue == value){
 arr.push(collection);
 }else{
 for(var elem in collection){
 gatherElements(collection[elem], key, value, arr);
 }
 }
 }else if(typeof collection == 'array'){
 for(var i = 0; i < collection.length; i++) {
 getKeyGroup(collection[i], key, value, arr);
 }
 }
}
function getKeyGroup(collection, key, keygroup){
 var targetValue = '';
 if(typeof collection == 'object'){
 targetValue = collection[key];
 if(typeof targetValue != 'undefined'){
 keygroup.push(targetValue);
 }else{
 for(var elem in collection){
 getKeyGroup(collection[elem], key, keygroup);
 }
 }
 }else if(typeof collection == 'array'){
 console.log('isArr');
 for(var i = 0; i < collection.length; i++) {
 getKeyGroup(collection[i], key, keygroup);
 }
 }
 return keygroup;
}
function main(){
 var test = {
 items : [
 {
 company : "A"
 , name : "Prod_A01"
 }
 , {
 company : "A"
 , name : "Prod_A02"
 }
 , {
 company : "B"
 , name : "Prod_B01"
 }
 ]
 }
 regroup(test, "company");
}

However, I think looping every time does not look so good. I need to improve this source code.

Answer 1

I think you may be complicating things a lot. If I understand correctly you are basically after groupBy which you can find in lodash, or implement in a few lines of code:

function groupBy(coll, f) {
 return coll.reduce(function(acc, x) {
 var k = f(x);
 acc[k] = (acc[k] || []).concat(x);
 return acc;
 }, {});
}
var test = {
 items: [{
 company: "A", name: "Prod_A01"
 }, {
 company: "A", name: "Prod_A02"
 }, {
 company: "B", name: "Prod_B01"
 }]
};
var result = groupBy(test.items, function(x){return x.company});
JSON.stringify(result);
/*^
{
 "A": [
 {
 "company": "A",
 "name": "Prod_A01"
 },
 {
 "company": "A",
 "name": "Prod_A02"
 }
 ],
 "B": [
 {
 "company": "B",
 "name": "Prod_B01"
 }
 ]
}
*/

You can use this to group a collection (array of objects) by some property, test.items in this case. Also, I would leave the JSON part out of it, because it is irrelevant to the grouping algorithm.

• Juneyoung Oh: wow. awesome! so simple!!
• Juneyoung Oh: Got one more question. You mentioned about lodash. Why did you mentioned that? (Your code seems work nicely with native js)
• elclanrs: Just because it is a popular library, you may use it and import only that function npmjs.com/package/lodash.groupby. Also in lodash it is a bit more flexible, you can do _.groupBy(test.items, 'company')