Convert an array of object to a new array of object with keys in javscript

March 25, 2022

I have an array of objects in the format below and would like to transform it into a new array of objects using a property as a key. The key should be unique. See shape of the object below

const mockedList = [
  {
    email: 'aaa@example.com',
    id: '5052',
    name: 'Java',
  },
  {
    email: 'bbb@example.com',
    id: '5053',
    name: 'Python',
  },
  {
    email: 'aaa@example.com',
    id: '5054',
    name: 'C#',
  },
  {
    email: 'bbb@example.com',
    id: '5055',
    name: 'Javascript',
  },
];

I would like to transform this and get an array of objects with keys and values in this format.

[
   {
      email: 'bbb@example.com',
      languages: [
         {
            email: 'bbb@example.com',
            id: '5055',
            name: 'Javascript',
         },
         {
            email: 'bbb@example.com',
            id: '5053',
            name: 'Python',
         },
     ]             
   },
   {
      email: 'aaa@example.com',
      languages: [
         {
            email: 'aaa@example.com',
            id: '5052',
            name: 'Java',
         },
        {
            email: 'aaa@example.com',
            id: '5054',
            name: 'C#',
        },
     ]
   }
]

I’ve tried using map-reduce

const result = mockedList.reduce((r, a) => {
  r[a.email] = r[a.email] || [];
  r[a.email].push(a);
  return r;
}, Object.create(null));

But did not get the right shape of data

>Solution :

You can do:

const mockedList = [{email: 'aaa@example.com',id: '5052',name: 'Java',},{email: 'bbb@example.com',id: '5053',name: 'Python',},{email: 'aaa@example.com',id: '5054',name: 'C#',},{ email: 'bbb@example.com', id: '5055', name: 'Javascript' },]

const mockedListHash = mockedList.reduce((a, c) => {
  a[c.email] = a[c.email] || { email: c.email, languages: [] }
  a[c.email].languages.push(c)
  return a
}, {})
const result = Object.values(mockedListHash)

console.log(result)

In case you want to clean the repeated emails within languages:

const mockedList = [{email: 'aaa@example.com',id: '5052',name: 'Java',},{email: 'bbb@example.com',id: '5053',name: 'Python',},{email: 'aaa@example.com',id: '5054',name: 'C#',},{ email: 'bbb@example.com', id: '5055', name: 'Javascript' },]

const mockedListHash = mockedList.reduce((a, c) => {
  a[c.email] = a[c.email] || { email: c.email, languages: [] }
  a[c.email].languages.push({
    id: c.id,
    name: c.name,
  })
  return a
}, {})
const result = Object.values(mockedListHash)

console.log(result)