Re-structuring an array of objects with Underscore

Question

Is it possible to re-structure the below array

[
    {"period":"2016-09-18","mp-demo-1":30},
    {"period":"2016-09-18","MP7":20},
    {"period":"2016-09-19","mp-demo-1":13},
    {"period":"2016-09-19","MP7":33},
    {"period":"2016-09-20","mp-demo-1":39},
    {"period":"2016-09-20","MP7":29}
]

into

[
    {"period":"2016-09-18","mp-demo-1":30,"MP7":20},
    {"period":"2016-09-19","mp-demo-1":13,"MP7":33},
    {"period":"2016-09-20","mp-demo-1":39,"MP7":29},
]

What I basically need is to remove duplicate entries by the key (period) and add the values containing in those objects in to a single object.

Will this be possible using underscore.js? Or is there another way of doing this using jQuery or any other library.

Nenad Vracar · Accepted Answer · 2016-09-27 11:51:21Z

5

You can do this with pure javascript with reduce() and Object.assign()

var data = [
  {"period":"2016-09-18","mp-demo-1":30},
  {"period":"2016-09-18","MP7":20},
  {"period":"2016-09-19","mp-demo-1":13},
  {"period":"2016-09-19","MP7":33},
  {"period":"2016-09-20","mp-demo-1":39},
  {"period":"2016-09-20","MP7":29}
];

var obj = {}
var result = data.reduce(function(r, o) {
  if (!obj[o.period]) {
    obj[o.period] = o;
    r.push(obj[o.period]);
  } else {
    Object.assign(obj[o.period], o);
  }
  return r;
}, []);

console.log(result)

To keep original data you can create clone of object with Object.assign()

var data = [
  {"period":"2016-09-18","mp-demo-1":30},
  {"period":"2016-09-18","MP7":20},
  {"period":"2016-09-19","mp-demo-1":13},
  {"period":"2016-09-19","MP7":33},
  {"period":"2016-09-20","mp-demo-1":39},
  {"period":"2016-09-20","MP7":29}
];

var obj = {}
var result = data.reduce(function(r, o) {
  if (!obj[o.period]) {
    obj[o.period] = Object.assign({}, o);
    r.push(obj[o.period]);
  } else {
    Object.assign(obj[o.period], o);
  }
  return r;
}, []);

console.log(result);
console.log(data);

edited Sep 27, 2016 at 11:51

answered Sep 27, 2016 at 11:00

Nenad Vracar

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3 Comments

georg Over a year ago

Note that this also modifies the original array.

Nenad Vracar Over a year ago

@georg Updated my answer with solution that keeps original data.

georg Over a year ago

This might work for the OP's data, but in general cloning via serialization is a terrible idea. See my answer for how to do that correctly - basically, you should use Object.assign({}, ...) when you encounter an object for the first time.

georg · Accepted Answer · 2016-09-27 11:08:36Z

with lodash:

data = [
    {"period":"2016-09-18","mp-demo-1":30},
    {"period":"2016-09-18","MP7":20},
    {"period":"2016-09-19","mp-demo-1":13},
    {"period":"2016-09-19","MP7":33},
    {"period":"2016-09-20","mp-demo-1":39},
    {"period":"2016-09-20","MP7":29}
];


res = _(data)
    .groupBy('period')
    .map(_.spread(_.merge))
    .value();

console.log(res)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.16.2/lodash.min.js"></script>

Vanilla ES6:

data = [
    {"period":"2016-09-18","mp-demo-1":30},
    {"period":"2016-09-18","MP7":20},
    {"period":"2016-09-19","mp-demo-1":13},
    {"period":"2016-09-19","MP7":33},
    {"period":"2016-09-20","mp-demo-1":39},
    {"period":"2016-09-20","MP7":29}
];

let map = new Map();

data.forEach(x => map.set(x.period,
    Object.assign(
        map.get(x.period) || {},
        x
)));

console.log([...map.values()])

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