How do I create a nested array from current array?

Question

how can I convert this array to a new nested array based on a value within the array

CURRENT ARRAY

[{
 name: 'John',
 review: 'Its great',
 book: 'Jungle Book'
},
{
 name: 'Steve',
 review: 'Learned a lot',
 book: 'Coding Standards'
},
{
 name: 'Chris',
 review: 'Love it',
 book: 'Coding Standards'
},
{
 name: 'Jake',
 review: 'Would read again',
 book: 'Jungle Book'
}]

LOOKING TO MAKE THIS NESTED ARRAY

[{
 book: 'Jungle Book',
 comment: [{
   name: 'Jake',
   review: 'Would read again'
  },
  {
   name: 'John',
   review: 'Its great'   
  }]
},
{
 book: 'Coding Standards',
 comment: [{
   name: 'Chris',
   review: 'Love it'
  },
  {
   name: 'Steve',
   review: 'Learned a lot'   
  }]
}]

Any help or tips would be greatly appreciated.

yes, what am i missing. Sorry but yes my goal is an nested array — Zeus
– Zeus, Commented Apr 2, 2020 at 15:17

palaѕн · Accepted Answer · 2020-04-02 15:16:57Z

3

Your expected result is not a valid one. I think comment here needs to be an array of object like:

const temp = [{name:"John",review:"Its great",book:"Jungle Book"},{name:"Steve",review:"Learned a lot",book:"Coding Standards"},{name:"Chris",review:"Love it",book:"Coding Standards"},{name:"Jake",review:"Would read again",book:"Jungle Book"}];

const res = Object.values(temp.reduce((ac, { name, review, book }) => {
  ac[book] = ac[book] || {book, comment: []}
  ac[book].comment.push({name, review})
  return ac;
}, {}));

console.log(res);

.as-console-wrapper { max-height: 100% !important; top: 0; }

answered Apr 2, 2020 at 15:16

palaѕн

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1 Comment

Zeus Over a year ago

This solution worked perfectly. Thank you for your help

Nicolae Maties · Accepted Answer · 2020-04-02 15:17:58Z

1

const arr = [{
 name: 'John',
 review: 'Its great',
 book: 'Jungle Book'
},
{
 name: 'Steve',
 review: 'Learned a lot',
 book: 'Coding Standards'
},
{
 name: 'Chris',
 review: 'Love it',
 book: 'Coding Standards'
},
{
 name: 'Jake',
 review: 'Would read again',
 book: 'Jungle Book'
}];


const result = arr.reduce(function (r, a) {
    r[a.book] = r[a.book] || [];
    r[a.book].push(a);
    return r;
}, Object.create(null));

console.log(result);

You can do what i've done above or use _.groupBy() from lodash.

answered Apr 2, 2020 at 15:17

Nicolae Maties

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1 Comment

Zeus Over a year ago

Good to know. didnt realize groupBy Lodash function

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