CODEWITHSUNDEEP
javascriptarraystypescriptobject
MarkD
MarkD

Reputation: 4944

Converting array of javascript objects to key-value pairs of arrays based on property using ES6

Lets say I have the following array of objects:

myArray = [
  {name: 'First', parent: 1, delta: 2},
  {name: 'Second', parent: 1, delta: 1},
  {name: 'Third', parent: 2, delta: 1}
];

I would like to convert this array to an object, with keys for the parent, and values of the objects. e.g.:

result = {
  1: [
       {name: 'First', parent: 1, delta: 2},
       {name: 'Second', parent: 1, delta: 1}
     ],
  2: [
       {name: 'Third', parent: 2, delta: 1}
     ]
}

I can do this using a forEach, or nested loops, but am wondering if there is a way using ES6 syntax to do this a bit more concise/inline, which would allow me to do things like sort on delta, etc.

Upvotes: 1

Views: 69

Answers (4)

Eugene Mihaylin
Eugene Mihaylin

Reputation: 1776

const result = myArray.reduce((result, el) => {
  if (result[el.parent]) result[el.parent].push(el);
  else result[el.parent] = [el];
  return result;
}, {});

Upvotes: 1

Nitish Narang
Nitish Narang

Reputation: 4184

You can use reduce to achieve this

var myArray = [
  {name: 'First', parent: 1, delta: 2},
  {name: 'Second', parent: 1, delta: 1},
  {name: 'Third', parent: 2, delta: 1}
];

var result = myArray.reduce((o,d) =>
             (
               o[d.parent] = (o[d.parent] || []).concat(d)
               , o
             )
             , {})
console.log(result)

Upvotes: 1

Ankit Agarwal
Ankit Agarwal

Reputation: 30739

You can use Array.reduce() for that:

let myArray = [{
    name: 'First',
    parent: 1,
    delta: 2
  },
  {
    name: 'Second',
    parent: 1,
    delta: 1
  },
  {
    name: 'Third',
    parent: 2,
    delta: 1
  }
];
var res = myArray.reduce((acc, item) => {
  if (acc[item.parent]) {
    acc[item.parent].push(item);
  } else {
    acc[item.parent] = [item];
  }
  return acc;
}, {});
console.log(res);

Upvotes: 2

Anurag Awasthi
Anurag Awasthi

Reputation: 6233

var myArray = [
  {name: 'First', parent: 1, delta: 2},
  {name: 'Second', parent: 1, delta: 1},
  {name: 'Third', parent: 2, delta: 1}
];

console.log(myArray.reduce((acc, val)=>({...acc, [val.parent]: (acc[val.parent] || []).concat(val)}), {}))

Upvotes: 1

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