I have a dictionary where key is string and value is array of objects:
objDict = {
dataset1: [ { id: 1, count: 6 }, { id: 2, count: 7 }, { id: 3, count: 8 } ],
dataset2: [ { id: 1, count: 5 }, { id: 2, count: 4 }, { id: 3, count: 3 } ]
}
I need to filter objects with specific id and create an array of count values: for id = 2 it would be countArray = [ 7, 4 ].
I suppose I should first use Object.values(objDict) but I don't know what to do afterwards.
Convert the object to an array with Object.values(), flatten to a single array, reduce and push the relevant count values to the accumulator (acc) array:
const getCountById = (id, dict) => Object.values(objDict)
.flat()
.reduce((acc, { id: oid, count }) => {
if(id === oid) acc.push(count)
return acc
}, [])
const objDict = {
dataset1: [ { id: 1, count: 6 }, { id: 2, count: 7 }, { id: 3, count: 8 } ],
dataset2: [ { id: 1, count: 5 }, { id: 2, count: 4 }, { id: 3, count: 3 } ]
}
const result = getCountById(2, objDict)
console.log(result)This is a bit of an abuse of reduce, the more idiomatic form would be to filter by the id, and then to map the objects to the count values:
const getCountById = (id, dict) => Object.values(objDict)
.flat()
.filter(o => o.id === id)
.map(o => o.count)
const objDict = {
dataset1: [ { id: 1, count: 6 }, { id: 2, count: 7 }, { id: 3, count: 8 } ],
dataset2: [ { id: 1, count: 5 }, { id: 2, count: 4 }, { id: 3, count: 3 } ]
}
const result = getCountById(2, objDict)
console.log(result)So for ease, you can chain the Object.values call with a reduce to get the desired results
Something like:
const countArray = Object.values(objDict)
.reduce((prev, curr) => {
return [...prev, ...curr.filter(el => el.id === 2).map(el => el.count)]
}, [])
Explanation
Object.values() in this case will return an array of arrays, so you will need to flatten those out, I did this by using the spread operator for the return of the filter() and map() chain. The filter is used as its name suggests to filter any value that passes the predicate function, and the map returns the correct format you were after.
You can also move the map from inside the reduce to chain the return value of the reduce if you wished. Like so:
const countArray = Object.values(objDict)
.reduce((prev, curr) => {
return [...prev, ...curr.filter(el => el.id === 2)]
}, [])
.map(el => el.count)