Convert nested Array -> arrays -> object TO Array -> Object => object value : object value

Question

In the data below. I would like to get it an object with some of the values as keys , like this:

FROM HERE: link to the whole data HERE (this.localObject)

const employees = [{
    "EmployeeID": "100A",
    "FirstName": "Downs",
    "aval": [
       {"start": "11-19", "end": "2", "ava": "30", "health": "4"},
       {"start": "11-20", "end": "2", "ava": "40", "health": "4"},
       {"start": "11-21", "end": "2", "ava": "50", "health": "4"},
       {"start": "11-22", "end": "2", "ava": "60", "health": "4"}
    ]
  },
  {
    "EmployeeID": "100B",
    "FirstName": "Mckenzie",
    "aval": [
       {"start": "11-19", "end": "2", "ava": "1", "health": "4"},
       {"start": "11-20", "end": "2", "ava": "2", "health": "4"},
       {"start": "11-21", "end": "2", "ava": "3", "health": "4"},
       {"start": "11-22", "end": "2", "ava": "4", "health": "4"}
    ]
  },
]

TO HERE:

const employees = [
   { "EmployeeID": "100A", "11-19": "30"},
   { "EmployeeID": "100A", "11-20": "40"},
   { "EmployeeID": "100A", "11-21": "50"},
   { "EmployeeID": "100A", "11-22": "60"},
   { "EmployeeID": "100B", "11-19": "1"},
   { "EmployeeID": "100B", "11-20": "2"},
   { "EmployeeID": "100B", "11-21": "3"},
   { "EmployeeID": "100B", "11-22": "4"}
]

//and so on...

So far I've tried:

this.localData = this.localObject.employees;
const firstLevel = this.localData.map(x => x.aval);

firsLevel will give me an array of objects which is closer to what I need, now I need to put the "start" value as a key and the "ava" value as a value property inside their own object containers

Nina Scholz · Accepted Answer · 2018-11-24 17:14:12Z

4

You need to iterate the inner arrays as well and build a single array.

var array = [{ EmployeeID: "100A", FirstName: "Downs", aval: [{ start: "11-19", end: "2", ava: "30", health: "4" }, { start: "11-20", end: "2", ava: "40", health: "4" }, { start: "11-21", end: "2", ava: "50", health: "4" }, { start: "11-22", end: "2", ava: "60", health: "4" }] }, { EmployeeID: "100B", FirstName: "Mckenzie", aval: [{ start: "11-19", end: "2", ava: "1", health: "4" }, { start: "11-20", end: "2", ava: "2", health: "4" }, { start: "11-21", end: "2", ava: "3", health: "4" }, { start: "11-22", end: "2", ava: "4", health: "4" }] }],
    result = array.reduce((r, { EmployeeID, aval }) => [
        ...r,
        ...aval.map(({ start, ava }) => ({ EmployeeID, [start]: ava }))
    ], []);

console.log(result);

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

answered Nov 24, 2018 at 17:14

Nina Scholz

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2 Comments

brohymn Over a year ago

Nice, may I ask any good sources to learn reduce() ?. it's not my forte

Nina Scholz Over a year ago

you could start here: Array#reduce, but i have no other resource than this. just try often to use it ...

Nitish Narang · Accepted Answer · 2018-11-24 17:12:37Z

2

You can use Array.flatMap and iterate over the aval inside it using Array.maplike below

const employees = [{
    "EmployeeID": "100A",
    "FirstName": "Downs",
    "aval": [
       {"start": "11-19", "end": "2", "ava": "30", "health": "4"},
       {"start": "11-20", "end": "2", "ava": "40", "health": "4"},
       {"start": "11-21", "end": "2", "ava": "50", "health": "4"},
       {"start": "11-22", "end": "2", "ava": "60", "health": "4"}
    ]
  },
  {
    "EmployeeID": "100B",
    "FirstName": "Mckenzie",
    "aval": [
       {"start": "11-19", "end": "2", "ava": "1", "health": "4"},
       {"start": "11-20", "end": "2", "ava": "2", "health": "4"},
       {"start": "11-21", "end": "2", "ava": "3", "health": "4"},
       {"start": "11-22", "end": "2", "ava": "4", "health": "4"}
    ]
  },
]

let res = employees.flatMap(({ EmployeeID, aval }) => 
                    aval.map(({ start, ava }) => ({ EmployeeID, [start]: ava })))

console.log(res)

answered Nov 24, 2018 at 17:12

Nitish Narang

4,2042 gold badges18 silver badges22 bronze badges

6 Comments

Nina Scholz Over a year ago

it looks like, you are a great fan of flatMap which does not work actually in edge ...

Nitish Narang Over a year ago

Oh yes I am (after understanding it's power). Given 'Edge' case, I doubt it supports other ESNext features as well at least some. But we should never miss any new feature because of just Edge. :)

brohymn Over a year ago

man, I love this answer, but the framework I'm using has a problem with ES6 and doesnt play well with FlatMap, they are working on the solution tho

Nitish Narang Over a year ago

No problem @brohymn. :)

georg Over a year ago

nice one... flatMap is trivial to polyfill

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