你会如何解决这个问题？使用reduce方法计算此数组中嵌套对象值的总和？
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【中文标题】你会如何解决这个问题？使用reduce方法计算此数组中嵌套对象值的总和？【英文标题】：How would you tackle this? using the reduce method to calculate the sum of a nested object value in this array? 【发布时间】：2022-01-18 08:03:48 【问题描述】：我需要找出这个数组中所有宠物的总年龄。我已经尝试过这段代码，但得到了一个 NaN 输出。我如何访问宠物的年龄以获得总和？
我尝试了这段代码，但得到了一个 NaN 输出。
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);有人能指出正确的方向吗？
【问题讨论】：
【参考方案1】：data 数组中的每个对象也有嵌套数组pets，因此您必须计算嵌套数组的总和并将其添加到全局计数中：
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);【讨论】：
【参考方案2】：一种方法可以如下所示：
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`);【讨论】：
curr?.pets?.forEach(( age ) => acc += age); 更干净。虽然两者都是一样的......
这是什么：curr?.pets? 是不是像["curr?"]["pets?"]？还是"?" 有什么特别之处？
@zer00ne "?"用于防止应用程序崩溃。在这种情况下，它将处理 curr 不是对象且 pets 不是数组或 curr 中不存在 pets 的情况。【参考方案3】：
使用.flatMap() 过滤掉所有非所有者：
data.flatMap(obj => obj.pets.length > 0 ? obj.pets : [])
您将获得一组pet 对象。接下来使用reduce得到所有pet.age的总和
.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);【讨论】：
【参考方案4】：另一种，只有一条线的解决方案：
const age = data.flatMap((o) => o.pets).reduce((acc, o) => acc + o.age, 0);
console.log(age) //126004497.005
【讨论】：
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