Merge objects in an array based on other values

Question

I'm trying to merge a set of strings in an array based on a series of matching properties and remove the items that were duplicates.

My current array:

{id: "12", value: "Option 1"},
{id: "55", value: "Option A"},
{id: "55", value: "Option B"},
{id: "55", value: "Option C"},
{id: "55", value: "Option D"},
{id: "106", value: "Option 1"}

I want to merge all items with the id of '55' so my array will look like this:

{id: "12", value: "Option 1"},
{id: "55", value: "Option A, Option B, Option C, Option D"},
{id: "106", value: "Option}

I can only manage to merge the first 2 items using a for loop and checking the -1 sibling and can't work out to do this without serious bloat to my code.

Any advice would be appreciated.

I was using almost exactly what Usman Rana posted (nested for loop) but I forgot the condition i != j and was getting irregularities. — Paul
– Paul, Commented Nov 3, 2017 at 7:21

Jonas Wilms · Accepted Answer · 2017-11-02 18:54:57Z

2

You may use an object as a lookup table while storing the results in an array in parallel:

const lookup = {}, result = [];

for( const {id, value} of input ){
  if(lookup[id]){
     lookup[id].value += "," + value;
  }else{
     result.push( lookup[id] = {id, value} );
  }
}

This is quite new javascript, but it works on modern engines ;)

edited Nov 2, 2017 at 18:54

answered Nov 2, 2017 at 18:47

Jonas Wilms

139k20 gold badges164 silver badges164 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Muhammad Usman · Accepted Answer · 2017-11-02 19:09:18Z

1

A bit late may be. But you can try this with for/while loop. It's a very basic approach. And if time complexity is not a concern. Otherwise Jons w's answer is good.

var x = [{id: "12", value: "Option 1"},
{id: "55", value: "Option A"},
{id: "55", value: "Option B"},
{id: "55", value: "Option C"},
{id: "55", value: "Option D"},
{id: "12", value: "Option D"},
{id: "53", value: "Option D"},
{id: "106", value: "Option 1"}];

for(var j =0; j<x.length;j++){
for(var i =0; i<x.length;i++){
  if(x[j].id == x[i].id && i !=j){
     x[j].value = x[j].value + "," +x[i].value;
     x.splice(i, 1);
     }
  }
}
console.log(x);

answered Nov 2, 2017 at 19:09

Muhammad Usman

10.1k26 silver badges41 bronze badges

2 Comments

Paul Over a year ago

Thanks Usman, I was trying a for loop with nested in a for loop but forgot about the i != j and was getting problems. I accepted the top answer as it's quite a small snippet of code but this is what I would have gone for originally.

Jonas Wilms Over a year ago

linting, linting, linting... And you need to decrement i after splicing... But still: thanks ;)

Hassan Imam · Accepted Answer · 2017-11-02 19:12:24Z

0

You can use array#reduce.

const data = [{id: "12", value: "Option 1"},{id: "55", value: "Option A"},{id: "55", value: "Option B"},{id: "55", value: "Option C"},{id: "55", value: "Option D"},{id: "106", value: "Option 1"}];

var result = data.reduce((r, o) => {
  return r[o.id] = r[o.id] ? (r[o.id].value += ", " + o.value, r[o.id]) : o, r;
},{})

var output = Object.values(result);
console.log(output);

.as-console-wrapper { max-height: 100% !important; top: 0; }

answered Nov 2, 2017 at 19:12

Hassan Imam

22.6k6 gold badges45 silver badges53 bronze badges

Collectives™ on Stack Overflow

Merge objects in an array based on other values

3 Answers 3

Comments

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related