merge array in deep array nodejs

Question

I have the following structure:

const array = [
  [
    [
      [
        [
          {
            'name':'John'
          }
        ],
        {
          'name':'Mary'
        }
      ],
      {
        'name':'Cris'
      }
    ],
    {
      'name':'Deen'
    }
  ],
  {
    'name':'Bob'
  }
]

And I'd like to get the following structure as a result:

const expect = [
  {
    'name':'John'
  },
  {
    'name':'Mary'
  },
  {
    'name':'Cris'
  },
  {
    'name':'Deen'
  },
  {
    'name':'Bob'
  },
]

How do I make such conversion with lodash or another library?

Not hard to find out how to flatten an array with limited web search time and some digging through lodash docs — charlietfl, Jun 24 '17 at 18:41
That's *not* merging, that is **flattening**. you confused the terms — vsync, Jun 25 '17 at 08:30
Possible duplicate of [Merge/flatten an array of arrays in JavaScript?](https://stackoverflow.com/questions/10865025/merge-flatten-an-array-of-arrays-in-javascript) — Mike Szyndel, Jun 25 '17 at 14:26

score 1 · Accepted Answer · answered Jun 24 '17 at 18:32

1

You could use _.flattenDeep from lodash:

Recursively flattens array.

const array = [[[[[{ name: 'John' }], { name: 'Mary' }], { name: 'Cris' }], { name: 'Deen' }], { name: 'Bob' }];
    
console.log(_.flattenDeep(array));

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

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.15.0/lodash.min.js"></script>

answered Jun 24 '17 at 18:32

Nina Scholz

351,820
24
303
358

I never thought I would see this day come O_O! – Rick Jun 24 '17 at 21:01
@Arrow, what do you mean? – Nina Scholz Jun 24 '17 at 21:03
You used lodash. Enemy to all higher order functions. – Rick Jun 24 '17 at 21:06
@Arrow, hm. the use does not justify the product. – Nina Scholz Jun 24 '17 at 21:14
@NinaSchotz O_o This is like seeing Superman use a gun. I will be scarred for life. – Rick Jun 24 '17 at 21:30
1

Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/147533/discussion-between-nina-scholz-and-arrow). – Nina Scholz Jun 24 '17 at 21:32

score 1 · Answer 2 · answered Jun 24 '17 at 18:33

You can create recursive function using reduce() to return desired result.

const array = [[[[[{"name":"John"}],{"name":"Mary"}],{"name":"Cris"}],{"name":"Deen"}],{"name":"Bob"}]

function flatten(arr) {
  return arr.reduce(function(r, e) {
     return r = r.concat(Array.isArray(e) ? flatten(e) : e), r
  }, [])
}

console.log(flatten(array))

score 1 · Answer 3 · answered Jun 24 '17 at 18:42

1

You can use this npm package npm underscore and this is a simple example: var _ = require('underscore-node'); var extractedArray = _.flatten(deepArray)

answered Jun 24 '17 at 18:42

Ninja

486
4
10

score 0 · Answer 4 · answered Jun 24 '17 at 18:40

function flattenArray(array, result) {
    result = result || [];
    for (var i = 0; i < array.length; i++) {
        if (Array.isArray(array[i])) {
            flattenArray(array[i], result);
        } else {
            result.push(array[i]);
        }
    }

    return result;
}

I wrote this some time back. Follows a recursive approach and is really fast as well.

JSPerf: https://jsperf.com/flatten-array-r1

score 0 · Answer 5 · answered Jun 24 '17 at 18:53

By pure ES6 and a Haskellesque pattern matching implemented by destructuring, you may simply do as follows;

function flat([a,...b]){
  return (Array.isArray(a) ? flat(a) : [a]).concat(b.length ? flat(b) : []);
}

var arr = [[[[[{"name":"John"}],{"name":"Mary"}],{"name":"Cris"}],{"name":"Deen"}],{"name":"Bob"}],
    res = flat(arr);
console.log(res);

Rick · Answer 6 · 2017-06-24T20:56:59.683

You can do it with closures and a single line of code with ES6. Libraries, when not necessary are a burden. Avoid them where you can.

const flatten = arr => arr.reduce((r, e) => (r = r.concat(Array.isArray(e) ? flatten(e) : e), r), []);

const array = [
  [
    [
      [
        [{
          'name': 'John'
        }],
        {
          'name': 'Mary'
        }
      ],
      {
        'name': 'Cris'
      }
    ],
    {
      'name': 'Deen'
    }
  ],
  {
    'name': 'Bob'
  }
];
console.log(flatten(array))

score 0 · Answer 7 · edited Jun 20 '20 at 09:12

Optimal way without any library and using good-old JS logic:

var arr = [
  [
    [
      [
        [
          {
            'name':'John'
          }
        ],
        {
          'name':'Mary'
        }
      ],
      {
        'name':'Cris'
      }
    ],
    {
      'name':'Deen'
    }
  ],
  {
    'name':'Bob'
  }
];

// convert to string and remove all Array "[" and "]" symbols
var str = JSON.stringify(arr).replace(/\[|]/g,'');
// convert the String back to an Object (Array)
var flatArr = JSON.parse("[" + str + "]");

console.log(flatArr)

vincent · Answer 8 · 2021-01-15T03:36:41.360

Consider using object-scan. It's powerful for doing in memory data structure processing (once you wrap your head around it).

Here is how you could solve your example

// const objectScan = require('object-scan');

const find = (input) => objectScan(['**'], {
  reverse: false,
  rtn: 'value',
  filterFn: ({ value }) => typeof value.name === 'string'
})(input);

const array = [[[[[{ name: 'John' }], { name: 'Mary' }], { name: 'Cris' }], { name: 'Deen' }], { name: 'Bob' }];

console.log(find(array));
// => [ { name: 'John' }, { name: 'Mary' }, { name: 'Cris' }, { name: 'Deen' }, { name: 'Bob' } ]

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

<script src="https://bundle.run/object-scan@13.8.0"></script>

Disclaimer: I'm the author of object-scan

merge array in deep array nodejs

8 Answers8

Optimal way without any library and using good-old JS logic: