Merge objects inside an array of objects with duplicates

Question

I have "available" data and want to convert it into "desired".

I tried to merge all objects inside array using this but its not working coz as you can see for timestamp = 10 we have 2 values of sw_version

const available = [
    {
      "timestamp": 10,
      "sw_version": "AA"
    },
    {
      "timestamp": 10,
      "sw_version": "AB"
    },
    {
      "timestamp": 20,
      "sw_version": "QFX-1.2.5 B"
    },
    {
      "timestamp": 10,
      "pressure": 14.75
    },
    {
      "timestamp": 20,
      "pressure": 14.22
    },
    {
      "timestamp": 10,
      "temperature": 15.96
    },
    {
      "timestamp": 20,
      "temperature": 38.50
    },
{
      "timestamp": 30,
      "temperature": 2.2
    },
    {
      "timestamp": 30,
      "pressure": 9.8
    }
  ]

const desired = [
    {
      "timestamp": 10,
      "sw_version": "AA",
      "pressure": 14.75,
      "temperature": 15.96
    },
    {
      "timestamp": 10,
      "sw_version": "AB",
      "pressure": 14.75,
      "temperature": 15.96
    },
    {
      "timestamp": 20,
      "sw_version": "QFX-1.2.5 B",
      "pressure": 14.22,
      "temperature": 38.5
    },
{
      "timestamp": 30,
      "pressure": 9.8,
      "temperature": 2.2
    }
  ]

const output = available.reduce((result, item) => {
      const i = result.findIndex((resultItem) => resultItem.timestamp === item.timestamp);
      if (i === -1) {
        result.push(item);
      } else {
        result[i] = { ...result[i], ...item };
      }
      return result;
    }, []);
    
console.log(output)

The output was

[
  {
    "timestamp": 10,
    "sw_version": "AB",
    "pressure": 14.75,
    "temperature": 15.96
  },
  {
    "timestamp": 20,
    "sw_version": "QFX-1.2.5 B",
    "pressure": 14.22,
    "temperature": 38.5
  },
  {
    "timestamp": 30,
    "temperature": 2.2,
    "pressure": 9.8
  }
]

As you can see in the desired output i want 2 objects with timestamp = 10 but in the function output its is overwriting the first one and keeping only one object.

We will get multiple values for same timestamp for only one measurement which is sw_version. For other measurements like temperature or pressure we won't get multiple values for same timestamps. sw_version is optional as well so we may get data where sw_version will not be there and we just have to merge without thinking about duplicating rows timestamp is mandatory it will always be there

I think you need to provide more rules as to how exactly merge here. E.g. what happens when you get a second value for pressure or temperature for a timestamp where you already have a measurement? Do you want to handle this the same way as for sw_version i. e. also have a separate object in the output for those? What happens if you receive the same measurement for the same timestamp twice e.g. m1 = { timestamp: 10, temp: 10 } and m2 = { timestamp: 10, temp: 10 }. Should these be one or two objects in the output? — Mushroomator
– Mushroomator, Commented Aug 13, 2024 at 17:03
please clarify your question: are the rows with sw_version are always the first in your initial array ? — Mister Jojo
– Mister Jojo, Commented Aug 13, 2024 at 17:05
Please clarify your question: is there some final line without timestamp or sw_version properties ? — Mister Jojo
– Mister Jojo, Commented Aug 13, 2024 at 17:10
@Mushroomator to answer your first question yes we might get second value for pressure or temperature for a timestamp where we already have a measurement just like sw_version Second question answer is no same measurement for the same timestamp twice will not happen. Hope this answers your question and thanks for asking — shamikh
– shamikh, Commented Aug 13, 2024 at 17:11
@MisterJojo Answer to both your question is No. sw_version can appear anywhere. and No row without timestamp is possible. Thanks — shamikh
– shamikh, Commented Aug 13, 2024 at 17:13

score 0 · Accepted Answer · 2024-08-13 18:29:28Z

First, I would group by timestamp and store all sw_version in an array. Then, I would create the expected structure for each sw_version for each timestamp. I would use a special case, if there is no sw_version.

const available = [{"timestamp": 10,"sw_version": "AA"},{"timestamp": 10,"sw_version": "AB"},{"timestamp": 20,"sw_version": "QFX-1.2.5 B"},{"timestamp": 10,"pressure": 14.75},{"timestamp": 20,"pressure": 14.22},{"timestamp": 10,"temperature": 15.96},{"timestamp": 20,"temperature": 38.50},{"timestamp": 30,"temperature": 2.2},{"timestamp": 30,"pressure": 9.8}];

const output = Object.entries(available.reduce((acc, el) => {
  if (!(el.timestamp in acc)) acc[el.timestamp] = {};
  if ("sw_version" in el) 
    if (!("sw_version" in acc[el.timestamp])) acc[el.timestamp].sw_version = [el.sw_version];
    else acc[el.timestamp].sw_version.push(el.sw_version);
  else
    acc[el.timestamp] = {...acc[el.timestamp], ...el};
  return acc;
}, {})).flatMap(([timestamp, el]) => !("sw_version" in el)
  ? el
  : el.sw_version.map(sw_version => ({
      ...el,
      sw_version
    }))
);

console.log(output);

Mister Jojo · Accepted Answer · 2024-08-13 18:50:29Z

0

it could be done this way :

const available = 
  [ { timestamp: 10, sw_version: 'AA'          }
  , { timestamp: 10, sw_version: 'AB'          }
  , { timestamp: 10, pressure:    14.75        } 
  , { timestamp: 20, pressure:    14.22        } 
  , { timestamp: 10, temperature: 15.96        } 
  , { timestamp: 20, temperature: 38.50        } 
  , { timestamp: 20, sw_version: 'QFX-1.2.5 B' } // off order
  , { timestamp: 30, temperature:  2.2         } 
  , { timestamp: 30, pressure:     9.8         } 
  ];

const result = available
  .filter( ({ sw_version }) => !sw_version )
  .reduce( (res, { timestamp, ...props }) =>
  {
  let rows = res.filter( elm => elm.timestamp === timestamp );

  if (!rows.length )
    res.push({timestamp,...props});
  else
    rows.forEach( line => Object.assign(line, props));  
 
  return res;
  }
  , available
     .filter( ({ timestamp:t, sw_version:v }) => !!t && !!v )
     .map( x => Object.assign({},x))
  );  

console.log( JSON.stringify(result,0,2))

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

edited Aug 13, 2024 at 18:50

answered Aug 13, 2024 at 17:40

Mister Jojo

22.9k6 gold badges28 silver badges45 bronze badges

4 Comments

shamikh Over a year ago

it fails if sw_version is not present for example [{ "timestamp": 20, "pressure": 14.22 } { "timestamp": 20, "temperature": 38.50 } ]

Mister Jojo Over a year ago

@Shaick : I've Asked you for this is there some final line without timestamp or sw_version properties and you'are responded no Why do you change this rule ?

shamikh Over a year ago

Sorry I was confused with the word 'final'. That's why i said No. I apologize for that. So Timestamp will always be there but sw_version is optional.

Mister Jojo Over a year ago

@shamikh final line mean any lines on your desired array. and all of them have a timestamp and a sw_version properties. If it is not the case you should edit your question with a really representatives case for input and output arrays, which is not the case actually.

Collectives™ on Stack Overflow

Merge objects inside an array of objects with duplicates

2 Answers 2

Comments

4 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

4 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related