Rewrite array based on child array javascript [closed]

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I have array of array like

{
  "campaigns": [{
      "name": "1st Campaign",
      "books": [{
          "title": "1st book",
          "primary_isbn": "isbn1"
        },
        {
          "title": "2nd book",
          "primary_isbn": "isbn2"
        },
        {
          "title": "3rd book",
          "primary_isbn": "isbn3"
        }
      ]
    },
    {
      "name": "2nd cam",
      "books": [{
          "title": "4th book",
          "primary_isbn": "isbn4"
        },
        {
          "title": "5th book",
          "primary_isbn": "isbn5"
        }
      ]
    }
  ]
}

From above array i need to create new array where each campaign (parent) data converted to number of items per book. So for first item 1st campaign should be converted to 3 items as there are 3 books. so my new array should be

{
  "campaigns": [{
      "name": "1st campaign"
      "title": "1st book",
      "primary_isbn": "isbn1"
    },
    {
      "name": "1st campaign"
      "title": "2nd book",
      "primary_isbn": "isbn2"
    },
    {
      "name": "1st campaign"
      "title": "3rd book",
      "primary_isbn": "isbn3"
    },
    ...
  ]
}

And same structure for 2nd campaign. I am not sure how to approach this problem

I tried this using lodash

_.flattenDeep(data.campaigns.books)

Do you have any attempts? Like finding books, campaigns etc. — Doğancan Arabacı
– Doğancan Arabacı, Commented Apr 19, 2019 at 12:35
jvm, you need to add in any code you've attempted to your question as minimal reproducible examples. It will likely use a loop of some kind, and access arrays/objects on each iteration to access the information. — Andy
– Andy, Commented Apr 19, 2019 at 12:37
I did try using lodash using _.flattenDeep(data.campaigns.books but that isn't helping — jvm
– jvm, Commented Apr 19, 2019 at 12:39
Where does "1st book", "2nd book" in the output come from? Or should that be computed based on the index? Why is primary_isbn different from the input? — adiga
– adiga, Commented Apr 19, 2019 at 12:39

adiga · Accepted Answer · 2019-04-19 12:50:14Z

4

You could use flatMap and map like this:

const input = {campaigns:[{name:"1st Campaign",books:[{title:"1st book",primary_isbn:"isbn1"},{title:"2nd book",primary_isbn:"isbn2"},{title:"3rd book",primary_isbn:"isbn3"}]},{name:"2nd cam",books:[{title:"4th book",primary_isbn:"isbn4"},{title:"5th book",primary_isbn:"isbn5"}]}]};

const campaigns = 
  input.campaigns.flatMap(({ name, books }) => books.map(b => ({ ...b, name })))

console.log({ campaigns })

answered Apr 19, 2019 at 12:50

adiga

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