How can I loop through this array of objects in javascript?

Question

I have an array of objects here:

const users = [
 {
 name: 'xyz',
 claims: [
 {"location": 'dallas',
 "id": '123'},
 {"location": 'frisco',
 "id": '123'},
 {"location": 'plano',
 "id": '123'},
 ]
 },
 {
 name: 'abc',
 claims: [
 {"location": 'richardson',
 "id": '123'},
 {"location": 'rowlett',
 "id": '123'},
 {"location": 'dallas',
 "id": '123'},
 ]
 },
 {
 name: 'adr',
 claims: [
 {"location": 'frisco',
 "id": '123'},
 {"location": 'irving',
 "id": '123'},
 {"location": 'dallas',
 "id": '123'},
 ]
 }
]

I want to get all the locations with dallas as the value. How can I do that? I know I would probably use a loop (maybe a forEach) but I am not exactly sure how I could get the values that I need. Would I use filter?

• AndrewL64: I want to get all the locations with dallas as the value <- What do you want to get exactly? The id?
• Joel Hager: You would use .filter(). When I get to a computer I'll get something mocked up for you.
• CherryDT: users.map(u => u.claims).flat().filter(c => c. location === 'dallas')

Answer 1

You can use flatMap to flatten the mapped array after filtering the locations which equal to dallas.

const users = [
 {
 name: 'xyz',
 claims: [
 {"location": 'dallas',
 "id": '123'},
 {"location": 'frisco',
 "id": '123'},
 {"location": 'plano',
 "id": '123'},
 ]
 },
 {
 name: 'abc',
 claims: [
 {"location": 'richardson',
 "id": '123'},
 {"location": 'rowlett',
 "id": '123'},
 {"location": 'dallas',
 "id": '123'},
 ]
 },
 {
 name: 'adr',
 claims: [
 {"location": 'frisco',
 "id": '123'},
 {"location": 'irving',
 "id": '123'},
 {"location": 'dallas',
 "id": '123'},
 ]
 }
]
const result = users.flatMap(u => u.claims.filter(c => c.location === 'dallas'))
console.log(result)

• aquile hollins: Thanks for this. I failed a interview for not knowing this lol I was trying to filter and that’s it. I see where I went wrong and I will never forget the use case for flatMap again!
• Mina: You are welcome, Never mind about the interview, and try to train on arrays high order methods, like flat, flatMap, filter, reduce, reduceRight, map, forEach, some, every and try to know the uses of each of them, and I wish you good luck in the next interview.

Answer 2

Use flatMap with combination of filter:

const dallasLocations = users.flatMap(user => {
 return user.claims.filter(claim => claim.location === 'dallas')
})