I need to convert the the init array to final array preferably using lodash.

initArray = [
   {
      "date":"2017-08-15",
      "data":[
         {
            "color":"orange",
            "count":100
         },
         {
            "color":"green",
            "count":101
         }
      ]
   },
   {
      "date":"2017-08-14",
      "data":[
         {
            "color":"orange",
            "count":102
         },
         {
            "color":"green",
            "count":103
         }
      ]
   }
]

finalArray = [
   {
      "color":"orange",
      "data":[
         100,
         102
      ]
   },
   {
      "color":"green",
      "data":[
         101,
         103
      ]
   }
]

I need to convert the the init array to final array preferably using lodash.

initArray = [
   {
      "date":"2017-08-15",
      "data":[
         {
            "color":"orange",
            "count":100
         },
         {
            "color":"green",
            "count":101
         }
      ]
   },
   {
      "date":"2017-08-14",
      "data":[
         {
            "color":"orange",
            "count":102
         },
         {
            "color":"green",
            "count":103
         }
      ]
   }
]

finalArray = [
   {
      "color":"orange",
      "data":[
         100,
         102
      ]
   },
   {
      "color":"green",
      "data":[
         101,
         103
      ]
   }
]

• javascript
• arrays
• json
• lodash

Share Improve this question Follow edited Aug 18, 2017 at 2:15 Dij 9,81844 gold badges2020 silver badges3535 bronze badges asked Aug 18, 2017 at 2:15 Sumit DhamejaSumit Dhameja 14122 silver badges99 bronze badges 1

• 1 lodash puzzles are fun and all, but next time try to explain what you tried and why it didn't work. – aaaaaa Commented Aug 18, 2017 at 3:42

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2 Answers 2

Sorted by: Reset to default 5

This way seems like the lodash calls make sense to me.

// var _ = require('lodash')

initArray = [
   {
      "date":"2017-08-15",
      "data":[
         {
            "color":"orange",
            "count":100
         },
         {
            "color":"green",
            "count":101
         }
      ]
   },
   {
      "date":"2017-08-14",
      "data":[
         {
            "color":"orange",
            "count":102
         },
         {
            "color":"green",
            "count":103
         }
      ]
   }
]

result = _(initArray)
    //.map('data')
    //.flatten()
    .flatMap('data') // instead of .map('data').flatten()
    .groupBy('color')
    .map((item, key) => ({
        color: key,
        count: _.map(item, 'count')
    }))
    .value()

console.log(result)

<script src="https://cdn.jsdelivr/lodash/4/lodash.min.js"></script>

you can use reduce to flatten the original array, so that all data arrays are on same level. Then use _.transform to get a temp object mapping colors to array of their counts. and then you can push things to finalArray using forEach.

var initArray = [
   {
  "date":"2017-08-15",
  "data":[
     {
        "color":"orange",
        "count":100
     },
     {
        "color":"green",
        "count":101
     }
  ]
   },
   {
  "date":"2017-08-14",
  "data":[
     {
        "color":"orange",
        "count":102
     },
     {
        "color":"green",
        "count":103
     }
  ]
   }
];
var finalArray = [];
var temp = _.transform(initArray.reduce((a,b) => a.data.concat(b.data)), 
                       (r, v) => (r[v.color] || (r[v.color] = [])).push(v.count), {});

_.forEach(temp, (v,k) => finalArray.push({color:k, count:v}));

console.log(finalArray);

<script src="https://cdn.jsdelivr/lodash/4/lodash.min.js"></script>