Javascript: Convert Array into Object [duplicate]

Question

i have array:

[
  ['a', 'b', 'c'],
  ['a', 'h', 'k'],
  ['c', 'd', 'e']
]

Is there a best way to convert it on object like this?

{
  a: [
       ['a', 'b', 'c'],
       ['a', 'h', 'k'],
     ],
  c: [
       ['c', 'd', 'e']
     ]
}

You can use any of the grouping questions like (Most efficient method to groupby on an array of objects or How to group an array of objects by key). Use '0' as the property you want to group by. — adiga
– adiga, Commented Feb 3, 2021 at 8:40
it is to merge all the ways elements have an equal array [0] into one key of the object — Kiều Toàn
– Kiều Toàn, Commented Feb 3, 2021 at 8:41

Nguyễn Văn Phong · Accepted Answer · 2021-02-03 09:32:03Z

2

You can achieve it by using .reduce & Logical nullish assignment (??=)

const arrays = [
  ['a', 'b', 'c'],
  ['a', 'h', 'k'],
  ['c', 'd', 'e']
];

const result = arrays.reduce((acc, curr) => {
  const key = curr[0];
  acc[key] ??= [];
  acc[key].push(curr);
  
  return acc;
}, {})

console.log(result);

edited Feb 3, 2021 at 9:32

answered Feb 3, 2021 at 9:10

Nguyễn Văn Phong

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Comments

Mohammad Usman · Accepted Answer · 2021-02-03 08:42:41Z

0

You can use .reduce() to get the desired output:

const data = [
  ['a', 'b', 'c'],
  ['a', 'h', 'k'],
  ['c', 'd', 'e']
];

const result = data.reduce((r, c) => {
  r[c[0]] = r[c[0]] || [];
  r[c[0]].push(c);
  return r;
}, {});

console.log(result);

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

answered Feb 3, 2021 at 8:42

Mohammad Usman

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2 Comments

Nguyễn Văn Phong Over a year ago

You should cache the c[0] into an individual variable named key to make your code less complex as well as avoid duplication codes :) Is that ok if I edit it? sir

Nguyễn Văn Phong Over a year ago

Also, you can make your code more concise like from r[c[0]] = r[c[0]] || []; to acc[key] ??= [];. Check my answer below if you like. Thanks sir :)

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