How would you tackle this? using the reduce method to calculate the sum of a nested object value in this array?

Question

I need to find the total combined age of all pets in this array. I have tried this code but get a NaN output. how do i access age of pets to get the sum?

I tried this code but get a NaN output.

const totalAgeAllPets = data.reduce((result, pet) => {
return result + pet.pets.age},0)
console.log(totalAgeAllPets)

 const data = [{ name: "mark", age: 27, from: "Chicago", pets: [], }, { name: "greg", age: 68, from: "Auburn", pets: [{ type: "rock", name: "herbert", age: 126003219, }, ], }, { name: "ken", age: 28, from: "Naperville", pets: [{ type: "cat", name: "colby", age: 1, }, { type: "dog", name: "charlie", age: 3, }, { type: "dog", name: "william riker", age: 1, }, { type: "dog", name: "thomas riker", age: 1, }, ], }, { name: "kristiana", age: 47, from: "Chicago", pets: [], }, { name: "bryan", age: 27, from: "Lincoln Park Zoo", pets: [{ type: "white tiger", name: "arthur", age: 3, }, { type: "silverback gorilla", name: "tommy", age: 4, }, { type: "guinea pig", name: "kirk", age: 1, }, { type: "hamster", name: "spock", age: 1, }, { type: "hamster", name: "sarek", age: 1, }, { type: "cat", name: "quark", age: 1, }, { type: "cat", name: "kira nerys", age: 1, }, ], }, { name: "anthony", age: 31, from: "Phoenix", pets: [], }, { name: "stephanie", age: 27, from: "Chicago", pets: [{ type: "dog", name: "midnight", age: 3, }, ], }, { name: "david p", age: 40, from: "Lancaster", pets: [{ type: "dog", name: "quinn", age: 8, }, ], }, { name: "patrick", age: 39, from: "Poway", pets: [{ type: "dog", name: "hazel", age: 7, }, { type: "cat", name: "fredy perlman", age: 13, }, ], }, { name: "david a", age: 32, from: "San Francisco", pets: [{ type: "monstera", name: "holey", age: 1, }, ], }, { name: "timm", age: 32, from: "Gainsville", pets: [{ type: "goldfish", name: "betsy", age: 4, }, ], }, { name: "conrad", age: 101, from: "Minneapolis", pets: [], }, { name: "nate", age: 14, from: "Boston", pets: [{ type: "cat", name: "rosie", age: 0.005, }, { type: "hermit crab", name: "kermit", age: 1, // 16 wow wtf }, { type: "dog", name: "ernie", age: 4, }, { type: "cat", name: "kendrick lamar jr", age: 6, }, { type: "cat", name: "guinan", age: 589, }, { type: "cat", name: "beverly", age: 1, }, ], }, { name: "temo", age: 25, from: "Osaka", pets: [{ type: "dog", name: "nacho", age: 1, }, { type: "dog", name: "belky", age: 1, }, { type: "dog", name: "janeway", age: 4, }, { type: "dog", name: "jean-luc", age: 12, }, { type: "monkey", name: "shin chan", age: 1, }, ], }, { name: "griffin", age: 22, from: "Chicago", pets: [{ type: "bearded dragon", name: "ferg", age: 3, }, ], }, { name: "eman", age: 20, from: "Lake in the Hills", pets: [{ type: "parakeet", name: "sunny", age: 400, }, { type: "parrot", name: "vic fontaine", age: 46, }, { type: "parrot", name: "worf", age: 48, }, { type: "cockatoo", name: "spockatoo", age: 33, }, ], }, { name: "jürgen", age: 28, from: "Chicago", pets: [{ type: "cat", name: "mija", age: 6, }, ], }, { name: "michele", age: 33, from: "Rome", pets: [{ type: "cat", name: "caesar", // "cheeto" age: 3, }, { type: "cat", name: "cleopatra", age: 3, }, { type: "cat", name: "tuvok", age: 10, }, { type: "turtle", name: "spock", age: 13, }, ], }, { name: "mitchell", age: 19, from: "Iowa City", pets: [{ type: "cat", name: "eddie", age: 7, }, ], }, { name: "reuben", age: 41, from: "Durham", pets: [{ type: "cat", name: "nico", age: 15, }, { type: "cat", name: "rocky", age: 5, }, ], }, { name: "fatima", age: 24, from: "Milwaukee", pets: [{ type: "snake", name: "reginald", age: 12, }, ], }, ]; const totalAgeAllPets = data.reduce((result, pet) => { return result + pet.pets.age; }, 0); console.log(totalAgeAllPets);

can someone point me in the right direction?

Answer 1

Each object in data array has also nested array pets , So you have to count sum of nested array and add it in global count as:

const totalAgeAllPets = data.reduce((result, pet) => {
  return result + pet.pets.reduce((a, p) => a + p.age, 0);
}, 0);
console.log(totalAgeAllPets);

 const data = [{ name: "mark", age: 27, from: "Chicago", pets: [], }, { name: "greg", age: 68, from: "Auburn", pets: [{ type: "rock", name: "herbert", age: 126003219, }, ], }, { name: "ken", age: 28, from: "Naperville", pets: [{ type: "cat", name: "colby", age: 1, }, { type: "dog", name: "charlie", age: 3, }, { type: "dog", name: "william riker", age: 1, }, { type: "dog", name: "thomas riker", age: 1, }, ], }, { name: "kristiana", age: 47, from: "Chicago", pets: [], }, { name: "bryan", age: 27, from: "Lincoln Park Zoo", pets: [{ type: "white tiger", name: "arthur", age: 3, }, { type: "silverback gorilla", name: "tommy", age: 4, }, { type: "guinea pig", name: "kirk", age: 1, }, { type: "hamster", name: "spock", age: 1, }, { type: "hamster", name: "sarek", age: 1, }, { type: "cat", name: "quark", age: 1, }, { type: "cat", name: "kira nerys", age: 1, }, ], }, { name: "anthony", age: 31, from: "Phoenix", pets: [], }, { name: "stephanie", age: 27, from: "Chicago", pets: [{ type: "dog", name: "midnight", age: 3, }, ], }, { name: "david p", age: 40, from: "Lancaster", pets: [{ type: "dog", name: "quinn", age: 8, }, ], }, { name: "patrick", age: 39, from: "Poway", pets: [{ type: "dog", name: "hazel", age: 7, }, { type: "cat", name: "fredy perlman", age: 13, }, ], }, { name: "david a", age: 32, from: "San Francisco", pets: [{ type: "monstera", name: "holey", age: 1, }, ], }, { name: "timm", age: 32, from: "Gainsville", pets: [{ type: "goldfish", name: "betsy", age: 4, }, ], }, { name: "conrad", age: 101, from: "Minneapolis", pets: [], }, { name: "nate", age: 14, from: "Boston", pets: [{ type: "cat", name: "rosie", age: 0.005, }, { type: "hermit crab", name: "kermit", age: 1, // 16 wow wtf }, { type: "dog", name: "ernie", age: 4, }, { type: "cat", name: "kendrick lamar jr", age: 6, }, { type: "cat", name: "guinan", age: 589, }, { type: "cat", name: "beverly", age: 1, }, ], }, { name: "temo", age: 25, from: "Osaka", pets: [{ type: "dog", name: "nacho", age: 1, }, { type: "dog", name: "belky", age: 1, }, { type: "dog", name: "janeway", age: 4, }, { type: "dog", name: "jean-luc", age: 12, }, { type: "monkey", name: "shin chan", age: 1, }, ], }, { name: "griffin", age: 22, from: "Chicago", pets: [{ type: "bearded dragon", name: "ferg", age: 3, }, ], }, { name: "eman", age: 20, from: "Lake in the Hills", pets: [{ type: "parakeet", name: "sunny", age: 400, }, { type: "parrot", name: "vic fontaine", age: 46, }, { type: "parrot", name: "worf", age: 48, }, { type: "cockatoo", name: "spockatoo", age: 33, }, ], }, { name: "jürgen", age: 28, from: "Chicago", pets: [{ type: "cat", name: "mija", age: 6, }, ], }, { name: "michele", age: 33, from: "Rome", pets: [{ type: "cat", name: "caesar", // "cheeto" age: 3, }, { type: "cat", name: "cleopatra", age: 3, }, { type: "cat", name: "tuvok", age: 10, }, { type: "turtle", name: "spock", age: 13, }, ], }, { name: "mitchell", age: 19, from: "Iowa City", pets: [{ type: "cat", name: "eddie", age: 7, }, ], }, { name: "reuben", age: 41, from: "Durham", pets: [{ type: "cat", name: "nico", age: 15, }, { type: "cat", name: "rocky", age: 5, }, ], }, { name: "fatima", age: 24, from: "Milwaukee", pets: [{ type: "snake", name: "reginald", age: 12, }, ], }, ]; const totalAgeAllPets = data.reduce((result, pet) => { return result + pet.pets.reduce((a, p) => a + p.age, 0); }, 0); console.log(totalAgeAllPets);

Answer 2

One approach can be as shown below:

 const data = [ { "name": "mark", "age": 27, "from": "Chicago", "pets": [] }, { "name": "greg", "age": 68, "from": "Auburn", "pets": [ { "type": "rock", "name": "herbert", "age": 126003219 } ] }, { "name": "ken", "age": 28, "from": "Naperville", "pets": [ { "type": "cat", "name": "colby", "age": 1 }, { "type": "dog", "name": "charlie", "age": 3 }, { "type": "dog", "name": "william riker", "age": 1 }, { "type": "dog", "name": "thomas riker", "age": 1 } ] }, { "name": "kristiana", "age": 47, "from": "Chicago", "pets": [] }, { "name": "bryan", "age": 27, "from": "Lincoln Park Zoo", "pets": [ { "type": "white tiger", "name": "arthur", "age": 3 }, { "type": "silverback gorilla", "name": "tommy", "age": 4 }, { "type": "guinea pig", "name": "kirk", "age": 1 }, { "type": "hamster", "name": "spock", "age": 1 }, { "type": "hamster", "name": "sarek", "age": 1 }, { "type": "cat", "name": "quark", "age": 1 }, { "type": "cat", "name": "kira nerys", "age": 1 } ] }, { "name": "anthony", "age": 31, "from": "Phoenix", "pets": [] }, { "name": "stephanie", "age": 27, "from": "Chicago", "pets": [ { "type": "dog", "name": "midnight", "age": 3 } ] }, { "name": "david p", "age": 40, "from": "Lancaster", "pets": [ { "type": "dog", "name": "quinn", "age": 8 } ] }, { "name": "patrick", "age": 39, "from": "Poway", "pets": [ { "type": "dog", "name": "hazel", "age": 7 }, { "type": "cat", "name": "fredy perlman", "age": 13 } ] }, { "name": "david a", "age": 32, "from": "San Francisco", "pets": [ { "type": "monstera", "name": "holey", "age": 1 } ] }, { "name": "timm", "age": 32, "from": "Gainsville", "pets": [ { "type": "goldfish", "name": "betsy", "age": 4 } ] }, { "name": "conrad", "age": 101, "from": "Minneapolis", "pets": [] }, { "name": "nate", "age": 14, "from": "Boston", "pets": [ { "type": "cat", "name": "rosie", "age": 0.005 }, { "type": "hermit crab", "name": "kermit", "age": 1 }, { "type": "dog", "name": "ernie", "age": 4 }, { "type": "cat", "name": "kendrick lamar jr", "age": 6 }, { "type": "cat", "name": "guinan", "age": 589 }, { "type": "cat", "name": "beverly", "age": 1 } ] }, { "name": "temo", "age": 25, "from": "Osaka", "pets": [ { "type": "dog", "name": "nacho", "age": 1 }, { "type": "dog", "name": "belky", "age": 1 }, { "type": "dog", "name": "janeway", "age": 4 }, { "type": "dog", "name": "jean-luc", "age": 12 }, { "type": "monkey", "name": "shin chan", "age": 1 } ] }, { "name": "griffin", "age": 22, "from": "Chicago", "pets": [ { "type": "bearded dragon", "name": "ferg", "age": 3 } ] }, { "name": "eman", "age": 20, "from": "Lake in the Hills", "pets": [ { "type": "parakeet", "name": "sunny", "age": 400 }, { "type": "parrot", "name": "vic fontaine", "age": 46 }, { "type": "parrot", "name": "worf", "age": 48 }, { "type": "cockatoo", "name": "spockatoo", "age": 33 } ] }, { "name": "jürgen", "age": 28, "from": "Chicago", "pets": [ { "type": "cat", "name": "mija", "age": 6 } ] }, { "name": "michele", "age": 33, "from": "Rome", "pets": [ { "type": "cat", "name": "caesar", "age": 3 }, { "type": "cat", "name": "cleopatra", "age": 3 }, { "type": "cat", "name": "tuvok", "age": 10 }, { "type": "turtle", "name": "spock", "age": 13 } ] }, { "name": "mitchell", "age": 19, "from": "Iowa City", "pets": [ { "type": "cat", "name": "eddie", "age": 7 } ] }, { "name": "reuben", "age": 41, "from": "Durham", "pets": [ { "type": "cat", "name": "nico", "age": 15 }, { "type": "cat", "name": "rocky", "age": 5 } ] }, { "name": "fatima", "age": 24, "from": "Milwaukee", "pets": [ { "type": "snake", "name": "reginald", "age": 12 } ] } ]; const totalAgeOfAllPets = data.reduce((acc, curr) => { curr?.pets?.forEach(({age}) => {acc = acc + age}); return acc; }, 0); console.log(`Total age of all pets: ${totalAgeOfAllPets}`);

Answer 3

Use .flatMap() to filter out all non-owners:

 data.flatMap(obj => obj.pets.length > 0? obj.pets: [])

You'll get an array of pet objects. Next use reduce to get the sum of all pet.age

.reduce((sum, pet) => sum + pet.age, 0);

 const data =[{name:"mark",age:27,from:"Chicago",pets:[]},{name:"greg",age:68,from:"Auburn",pets:[{type:"rock",name:"herbert",age:126003219}]},{name:"ken",age:28,from:"Naperville",pets:[{type:"cat",name:"colby",age:1},{type:"dog",name:"charlie",age:3},{type:"dog",name:"william riker",age:1},{type:"dog",name:"thomas riker",age:1}],},{name:"kristiana",age:47,from:"Chicago",pets:[]},{name:"bryan",age:27,from:"Lincoln Park Zoo",pets:[{type:"white tiger",name:"arthur",age:3},{type:"silverback gorilla",name:"tommy",age:4},{type:"guinea pig",name:"kirk",age:1},{type:"hamster",name:"spock",age:1},{type:"hamster",name:"sarek",age:1},{type:"cat",name:"quark",age:1},{type:"cat",name:"kira nerys",age:1}]},{name:"anthony",age:31,from:"Phoenix",pets:[]},{name:"stephanie",age:27,from:"Chicago",pets:[{type:"dog",name:"midnight",age:3}]},{name:"david p",age:40,from:"Lancaster",pets:[{type:"dog",name:"quinn",age:8}]},{name:"patrick",age:39,from:"Poway",pets:[{type:"dog",name:"hazel",age:7},{type:"cat",name:"fredy perlman",age:13}]},{name:"david a",age:32,from:"San Francisco",pets:[{type:"monstera",name:"holey",age:1}]},{name:"timm",age:32,from:"Gainsville",pets:[{type:"goldfish",name:"betsy",age:4}]},{name:"conrad",age:101,from:"Minneapolis",pets:[]},{name:"nate",age:14,from:"Boston",pets:[{type:"cat",name:"rosie",age:0.005},{type:"hermit crab",name:"kermit",age:1},{type:"dog",name:"ernie",age:4},{type:"cat",name:"kendrick lamar jr",age:6},{type:"cat",name:"guinan",age:589},{type:"cat",name:"beverly",age:1}]},{name:"temo",age:25,from:"Osaka",pets:[{type:"dog",name:"nacho",age:1},{type:"dog",name:"belky",age:1},{type:"dog",name:"janeway",age:4},{type:"dog",name:"jean-luc",age:12},{type:"monkey",name:"shin chan",age:1}]},{name:"griffin",age:22,from:"Chicago",pets:[{type:"bearded dragon",name:"ferg",age:3}]},{name:"eman",age:20,from:"Lake in the Hills",pets:[{type:"parakeet",name:"sunny",age:400},{type:"parrot",name:"vic fontaine",age:46},{type:"parrot",name:"worf",age:48},{type:"cockatoo",name:"spockatoo",age:33}]},{name:"jürgen",age:28,from:"Chicago",pets:[{type:"cat",name:"mija",age:6}]},{name:"michele",age:33,from:"Rome",pets:[{type:"cat",name:"caesar",age:3},{type:"cat",name:"cleopatra",age:3},{type:"cat",name:"tuvok",age:10},{type:"turtle",name:"spock",age:13}]},{name:"mitchell",age:19,from:"Iowa City",pets:[{type:"cat",name:"eddie",age:7},]},{name:"reuben",age:41,from:"Durham",pets:[{type:"cat",name:"nico",age:15},{type:"cat",name:"rocky",age:5}]},{name:"fatima",age:24,from:"Milwaukee",pets:[{type:"snake",name:"reginald",age:12}]}]; const totalAgeAllPets = data.flatMap(obj => obj.pets.length > 0? obj.pets: []).reduce((sum, pet) => sum + pet.age, 0); console.log(totalAgeAllPets);

Answer 4

Another, just one line solution:

const age = data.flatMap((o) => o.pets).reduce((acc, o) => acc + o.age, 0);
console.log(age) //126004497.005