Javascript reduce array of object into one object with keys

Question

Hello i am trying to repack array of objects and convert it into one object with specific keys. So here is array:

 const entryPenaltyGroups = [
      { entryId: 16, intervalId: 8, penaltyTime: 16000 },
      { entryId: 16, intervalId: 10, penaltyTime: 6000 }
 ]

Expected result should be:

{
   '8': {
     penaltyTime: 16000
   },
   '10': {
     penaltyTime: 6000
   }
}

I have tried something with map(), but not getting expected results.

   for (const entry of entryPenaltyGroups) {
        entry.map(x => [{
          [x.intervalId]: {
             penaltyTime: x.intervalId
          },
        }])
    }

Should i use reduce() instead maybe?

What's your expected outcome when two items have the same intervalId ? — malarres
– malarres, Commented Feb 2, 2022 at 11:54
Why Object.keys() with an array? Why for...of...? Why .map() in the for...of... loop? Why .map() for a single element? And why is there no TypeError in your question that will be thrown by calling .map() on an object (entryPenaltyGroups[key].map(...))? -> How do I ask a good question? — Andreas
– Andreas, Commented Feb 2, 2022 at 11:55

Stuart · Accepted Answer · 2022-02-02 13:59:21Z

2

You can map the array into [key, value] pairs, and then use Object.fromEntries to convert the mapped array into a single object:

Object.fromEntries(entryPenaltyGroups.map(
    ({intervalId, penaltyTime}) => [intervalId, {penaltyTime}]
))

Alternatively:

Object.fromEntries(entryPenaltyGroups.map(
    entry => [entry.intervalId, {penaltyTime: entry.penaltyTime}]
))

If there are any duplicate keys, the last occurrence will be used in the resulting object.

edited Feb 2, 2022 at 13:59

answered Feb 2, 2022 at 11:55

Stuart

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Comments

rosmak · Accepted Answer · 2022-02-02 11:55:12Z

0

const entryPenaltyGroups = [
      { entryId: 16, intervalId: 8, penaltyTime: 16000 },
      { entryId: 16, intervalId: 10, penaltyTime: 6000 }
]
const formatted = {}
for(entry of entryPenaltyGroups){
      formatted[entry.intervalId] = {penaltyTime: entry.penaltyTime}
}
console.log(formatted)

answered Feb 2, 2022 at 11:55

rosmak

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Comments

Aleks · Accepted Answer · 2022-02-02 11:55:18Z

0

entryPenaltyGroups.reduce((acc, el)=>((acc[el.intervalId] = el.penaltyTime),acc),{})

answered Feb 2, 2022 at 11:55

Aleks

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Comments

malarres · Accepted Answer · 2022-02-02 11:59:06Z

0

A solution with reduce. This will override the item if they have the same intervalId , but OP commented that this is not a problem for them

const entryPenaltyGroups = [
      { entryId: 16, intervalId: 8, penaltyTime: 16000 },
      { entryId: 16, intervalId: 10, penaltyTime: 6000 }
 ]
 
 const result = entryPenaltyGroups.reduce( (acc,cur) => {
    acc[cur.intervalId] = {penaltyTime: cur.penaltyTime};
    return acc;
 }
 ,{})
 
 
 
 console.log(result)

answered Feb 2, 2022 at 11:59

malarres

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