how to access a specific field in a nested javascript array

Question

I'm struggling with understanding how to access a particular value that is in a nested array. Here's the data structure:

var data = [{id: "Game 1", count:[{date: datevalues, metric: values}] ,  rank: [{date: datevalues, metric: values}] },
{id: "Game 2", count: [{date: datevalues, metric: values}] ,  rank: [{date: datevalues, metric: values}] },
{id: "Game 3", count: [{date: datevalues, metric: values}] ,  rank: [{date: datevalues, metric: values}] },
{id: "Game 4", count: [{date: datevalues, metric: values}] ,  rank: [{date: datevalues, metric: values}] }]

Inside the array under both the count and rank keys are dictionaries with date and metric values, so going further, it looks like this:

[{date: "2017-01-01", metric: 100},
{date: "2018-01-01", metric: 90]...}]

My question is how do i directly access the date and metric fields?

Does this answer your question? How can I access and process nested objects, arrays or JSON? ALSO: stackoverflow.com/questions/64050793/… Also, when asking question add real sample data and wanted result so we know what are you trying to achieve , not guess — ikiK
– ikiK, Commented Mar 4, 2021 at 20:42

Eldar · Accepted Answer · 2021-03-05 06:13:21Z

1

You can use Array.map, spread and Array.flat combined like below :

const datevalues = "2017-01-01";
const values = 1; 
var data = [{id: "Game 1", count:[{date: datevalues, metric: values}] ,  rank: [{date: datevalues, metric: values}] },
{id: "Game 2", count: [{date: datevalues, metric: values}] ,  rank: [{date: datevalues, metric: values}] },
{id: "Game 3", count: [{date: datevalues, metric: values}] ,  rank: [{date: datevalues, metric: values}] },
{id: "Game 4", count: [{date: datevalues, metric: values}] ,  rank: [{date: datevalues, metric: values}] }]

const mapped = data.map(r=> [...r.count,...r.rank]).flat()

const mappedWithIds = data.map(r=> [...r.count.map(q=> ({id:r.id,...q})),
                                    ...r.rank.map(q=> ({id:r.id,...q}))])
                                    .flat()

console.log(mapped)
console.log(mappedWithIds)

edited Mar 5, 2021 at 6:13

answered Mar 4, 2021 at 20:42

Eldar

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2 Comments

TX412 Over a year ago

Thanks @Eldar, this worked perfectly. Just as an aside, is there a way to keep the id value with the flattened structure?

Eldar Over a year ago

@Travis1585 yes there is a way which is to use the Array.map to pass the id value to the inner array. See the updated answer.

Avedis Maroukian · Accepted Answer · 2021-03-04 20:44:07Z

0

You will need to have the id of the game. And then by getting the list of counts & ranks do a map for getting all the values from it.

const dates = data.filter(x => x.id)[0].count.map(x => x.date)
const metrics = data.filter(x => x.id)[0].count.map(x => x.metric)

answered Mar 4, 2021 at 20:44

Avedis Maroukian

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