Take unique and new values from the array with duplicate data

Question

Hi guys I have this scenario:

const data = [
    {
       "name": "Hebert",
       "timestamp": 1640371815, // 15:50:15
    },{
       "name": "Brien",
       "timestamp": 1640373855, // 16:24:15
    },{
       "name": "Hebert",
       "timestamp": 1640363601 // 13:33:21 
    },{
       "name": "Mary",
       "timestamp": 1640356701 // 11:38:21
    },{
       "name": "Mary",
       "timestamp": 1640356521 // 11:35:21 
    },{
       "name": "Mary",
       "timestamp": 1640356401 // 11:33:21
   }
];

I need to get lasted one from duplicates by timestamp:

   // expected result
    [
       {
         "name": "Hebert",
         "timestamp": 1640371815 // 15:50:15 newest one
       },{
         "name": "Brien",
         "timestamp": 1640373855 // 16:24:15 unique
       },{
         "name": "Mary",
         "timestamp": 1640356701 // 11:38:21 newest
       }
    ];

I try this:

    data.sort((a,b) => a.name.localeCompare(b.name))
        .filter((chat, index, self) => self.findIndex( c => c.name == chat.name ) == index )

output duplicated removed but no considering newest timestamp between each duplicates

Sort by timestamp first

yaakov
– yaakov

2021-12-24 20:33:06 +00:00
Commented Dec 24, 2021 at 20:33 — yaakov
– yaakov, Commented Dec 24, 2021 at 20:33

charlietfl · Accepted Answer · 2021-12-24 20:46:59Z

Rather than sorting and using filter you can iterate the array just once storing items in a Map or object using the names as keys and then just update the lowest timestamp as you loop through each item.

Then finally convert the object values back to array

const items = new Map()

data.forEach(({name,timestamp}) => {  
  const o = items.get(name);
  if(o){
    timestamp < o.timestamp && o.timestamp = timestamp;    
  } else {
     items.set(name, {name, timestamp});
  }
});

const res = [...items.values()]

console.log(res)

<script>

const data = [
    {
       "name": "Hebert",
       "timestamp": 1640371815, // 15:50:15
    },{
       "name": "Brien",
       "timestamp": 1640373855, // 16:24:15
    },{
       "name": "Hebert",
       "timestamp": 1640363601 // 13:33:21 
    },{
       "name": "Mary",
       "timestamp": 1640356701 // 11:38:21
    },{
       "name": "Mary",
       "timestamp": 1640356521 // 11:35:21 
    },{
       "name": "Mary",
       "timestamp": 1640356401 // 11:33:21
   }
];
</script>

Vektor · Accepted Answer · 2021-12-24 21:05:18Z

const data = [
    {
       "name": "Hebert",
       "timestamp": 1640371815, // 15:50:15
    },{
       "name": "Brien",
       "timestamp": 1640373855, // 16:24:15
    },{
       "name": "Hebert",
       "timestamp": 1640363601 // 13:33:21 
    },{
       "name": "Mary",
       "timestamp": 1640356701 // 11:38:21
    },{
       "name": "Mary",
       "timestamp": 1640356521 // 11:35:21 
    },{
       "name": "Mary",
       "timestamp": 1640356401 // 11:33:21
   }
];

const seen = {};
const dataModified = [];

data.forEach((elem) => {
  const index = seen[elem.name];
  
  if(index == undefined){
    dataModified.push(elem);
    seen[elem.name] = dataModified.length - 1;
  } else if(dataModified[index].timestamp < elem.timestamp){
    dataModified.splice(index, 1, elem);
  }
});

console.log(dataModified);

sandeep.kgp · Accepted Answer · 2021-12-24 21:08:00Z

0

data.sort((a,b) => a.name.localeCompare(b.name))
.filter((chat, index, self) => self.findIndex(c => c.name === chat.name && c.timestamp > chat.timestamp)<0)

The idea is that findIndex would only return the index when there exists another duplicate with greater timestamp, else it'd return -1.

edited Dec 24, 2021 at 21:08

answered Dec 24, 2021 at 21:02

sandeep.kgp

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