lodash to find common values from array of objects

Question

Find common values from Array of Objects and Transom them

tried using lodash groupBy

var data =[
  {
    "dc": 1,
    "effDate": "1/2/2019",
    "expDate": "1/2/2019",
    "rate": 1,
    "minCharge": 2
  },
  {
    "dc": 1,
    "effDate": "1/2/2019",
    "expDate": "1/2/2019",
    "rate": 2,
    "minCharge": 6
  },
  {
    "dc": 1,
    "effDate": "1/2/2019",
    "expDate": "1/2/2019",
    "rate": 4,
    "minCharge": 7
  }
]

var expectedResult=[
  {
    "dc": 1,
    "effDate": "1/2/2019",
    "expDate": "1/2/2019",
    "rateCharge": [
      {
        "rate": 1,
        "minCharge": 2
      },
      {
        "rate": 2,
        "minCharge": 6
      },
      {
        "rate": 4,
        "minCharge": 7
      }
    ]
  }
]

in data dc,effDate,expDate are same, so i need to keep common things as flat structure and move repeating items into rateCharge.

var expectedResult=uniqBy(data,(val1.rate,val2.rate) => {
  val1.rate!=val2.rate;    
});

I have tried using lodash uniqBy property but i am not getting expected result.

Ori Drori · Accepted Answer · 2019-02-06 17:18:08Z

2

You need to group the items by the effDate, and then map the groups to the required form using _.pick() / _.omit() , _.map(), and using _.uniqBy() with the rate as the unique identifier.

Typescript example (open the browsers console)

const { flow, partialRight: pr, groupBy, map, head, pick, omit, uniqBy } = _

const EFF_DATA = 'effDate'
const baseProps = ['dc', EFF_DATA, 'expDate']

const fn = flow(
  pr(groupBy, EFF_DATA),
  pr(map, g => ({
    ...pick(head(g), baseProps),
    rateCharge: uniqBy(map(g, pr(omit, baseProps)), 'rate')
  }))
)

const data = [{"dc":1,"effDate":"1/2/2019","expDate":"1/2/2019","rate":1,"minCharge":2},{"dc":1,"effDate":"1/2/2019","expDate":"1/2/2019","rate":2,"minCharge":6},{"dc":1,"effDate":"1/2/2019","expDate":"1/2/2019","rate":4,"minCharge":7}]

const result = fn(data)

console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.min.js"></script>

If you already import the entire lodash packages, you can use chaining:

const { flow, partialRight: pr, groupBy, map, head, pick, omit, uniqBy } = _

const EFF_DATA = 'effDate'
const baseProps = ['dc', EFF_DATA, 'expDate']

const data = [{"dc":1,"effDate":"1/2/2019","expDate":"1/2/2019","rate":1,"minCharge":2},{"dc":1,"effDate":"1/2/2019","expDate":"1/2/2019","rate":2,"minCharge":6},{"dc":1,"effDate":"1/2/2019","expDate":"1/2/2019","rate":4,"minCharge":7}]

const result = _(data)
  .groupBy(EFF_DATA)
  .map(g => ({
    ...pick(head(g), baseProps),
    rateCharge: uniqBy(map(g, pr(omit, baseProps)), 'rate')  
  }));

console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.min.js"></script>

And the lodash/fp version:

const { flow, groupBy, map, head, pick, omit, uniqBy, assoc } = _;

const EFF_DATA = 'effDate'
const baseProps = ['dc', EFF_DATA, 'expDate'];

const fn = flow(
  groupBy(EFF_DATA),
  map(g => assoc(
    'rateCharge',
    flow(map(omit(baseProps)), uniqBy('rate'))(g),
    pick(baseProps, head(g))
  ))
)

const data = [{"dc":1,"effDate":"1/2/2019","expDate":"1/2/2019","rate":1,"minCharge":2},{"dc":1,"effDate":"1/2/2019","expDate":"1/2/2019","rate":2,"minCharge":6},{"dc":1,"effDate":"1/2/2019","expDate":"1/2/2019","rate":4,"minCharge":7}]

const result = fn(data)

console.log(result)

<script src='https://cdn.jsdelivr.net/g/lodash@4(lodash.min.js+lodash.fp.min.js)'></script>

edited Feb 6, 2019 at 17:18

answered Feb 5, 2019 at 21:03

Ori Drori

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15 Comments

Mulan Over a year ago

lodash/fp exists so you don't have to pr everything

Ori Drori Over a year ago

Unfortunately, most users don't use lodash/fp yet. I usually add a lodash/fp solution as well, which I'll do soon.

Mulan Over a year ago

Nice update. Maybe mention how this works because you're stringing all of the values together with - to make a grouping key. And maybe mention how using - will cause an odd behaviour if the values may possibly contain -. Maybe too much to mention how a custom data type could support real compound data equality :D

Mithun S Over a year ago

What is underscore means? How can i use the same using lodash with angular(typescript)? Any difference in syntax? Please help

Ori Drori Over a year ago

Instead of destructuring the underscore, in angular you will import the various functions from lodash (or lodash/fp). That's the main difference in syntax.

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