JavaScript shortest way to map an array of objects to a new array of new objects?

Question

I have an array of person objects, where each person have an array of profiles objects which consist of name and an image url, and a list of addresses objects which consist of lat and long properties, as follows:

var listOfPersons = [{
    addresses : [{lat:11, long:11}, {lat:22, long:22}],
    profile: [{image:"some_url1", name: "peter parker"}]
},
{
    addresses : [{lat:33, long:33}, {lat:44, long:44}],
    profile: [{image:"some_url2", name: "bruce wayne"}]
}];

I need to create a new array of objects, where each new object has an image , long , lat properties, for each set of lat long , as follows:

var expectedResult = [
{
    image:"some_url1",
  lat:11,
  long:11
},
{
    image:"some_url1",
  lat:22,
  long:22
},
{
    image:"some_url1",
  lat:33,
  long:33
},
{
    image:"some_url1",
  lat:44,
  long:44
}
];

What is the shortest way (in terms of writing code) to map \\ reduce the first array into the second?

Answer 1

You can use nested Array.flatMap() with Array.map() to iterate the array/address/profiles, and combine image and lat , long properties into a single object:

 const listOfPersons = [{"addresses":[{"lat":11,"long":11},{"lat":22,"long":22}],"profile":[{"image":"some_url1","name":"peter parker"}]},{"addresses":[{"lat":33,"long":33},{"lat":44,"long":44}],"profile":[{"image":"some_url2","name":"bruce wayne"}]}]; const result = listOfPersons.flatMap(o => o.addresses.flatMap(({ lat, long }) => o.profile.map(({ image }) => ({ image, lat, long })) ) ); console.log(result);

If you always use just the 1st profile always, you can remove one level of Array.flatMap() :

 const listOfPersons = [{"addresses":[{"lat":11,"long":11},{"lat":22,"long":22}],"profile":[{"image":"some_url1","name":"peter parker"}]},{"addresses":[{"lat":33,"long":33},{"lat":44,"long":44}],"profile":[{"image":"some_url2","name":"bruce wayne"}]}]; const result = listOfPersons.flatMap(o => o.addresses.map(({ lat, long }) => ({ image: o.profile[0].image, lat, long })) ); console.log(result);

Answer 2

You can use Array.prototype.reduce() with combined Array.prototype.forEach() .

The documentation states for reduce() :

The reduce() method executes a reducer function (that you provide) on each element of the array, resulting in a single output value.

I think the following can work for you:

 const listOfPersons = [{ addresses : [{lat:11, long:11}, {lat:22, long:22}], profile: [{image:"some_url1", name: "peter parker"}] }, { addresses : [{lat:33, long:33}, {lat:44, long:44}], profile: [{image:"some_url2", name: "bruce wayne"}] }]; const result = listOfPersons.reduce((acc, cur) => { cur.addresses.forEach(e => acc.push({ ...e, image: cur.profile[0].image })); return acc; }, []); console.log(result);

I hope that helps!

Answer 3

Sinced you asked for shortest in writing code:

 var listOfPersons = [{addresses: [{lat:11, long:11}, {lat:22, long:22}],profile: [{image:"some_url1", name: "peter parker"}]},{addresses:lat:33, long:33}, {lat:44, long:44}],profile: [{image:"some_url2", name: "bruce wayne"}]}]; const res = listOfPersons.reduce((r,{addresses:a,profile:[{image}]})=> [...r,...a.map(o=>({image,...o}))],[]); console.log(res);

Here's with formatting and better variable names:

 var listOfPersons = [{ addresses : [{lat:11, long:11}, {lat:22, long:22}], profile: [{image:"some_url1", name: "peter parker"}] }, { addresses : [{lat:33, long:33}, {lat:44, long:44}], profile: [{image:"some_url2", name: "bruce wayne"}] }]; const res = listOfPersons.reduce((acc, { addresses: adr, profile: [{image}] }) => [...acc, ...adr.map(a => ({image, ...a}) )], []); console.log(res);

Answer 4

var listOfPersons = [
  {
    addresses: [{ lat: 11, long: 11 }, { lat: 22, long: 22 }],
    profile: [{ image: "some_url1", name: "peter parker" }]
  },
  {
    addresses: [{ lat: 33, long: 33 }, { lat: 44, long: 44 }],
    profile: [{ image: "some_url2", name: "bruce wayne" }]
  }
];

var expectedResult = listOfPersons.reduce(
  (acc, person) => ([
    ...acc,
    ...person.addresses.map(
      address => ({ ...address, image: person.profile[0].image })
    )
  ]),
  []
)

This will give you what you want assuming you always want the first result from .profile

Answer 5

var listOfPersons = [{
    addresses : [{lat:11, long:11}, {lat:22, long:22}],
    profile: [{image:"some_url1", name: "peter parker"}]
},
{
    addresses : [{lat:33, long:33}, {lat:44, long:44}],
    profile: [{image:"some_url2", name: "bruce wayne"}]
}];


var expectedResult = [];
expectedResult.forEach(person => {
    person.addresses.forEach(address => expectedResult.push({image: person.profile[0].image, ...address}))
});