How to get all the values from multiple keys of an array of object?

Question

I need to get values from multiple keys from an array of object.

trip = [
    {sp: 'cbe', ep: 'tpr'}, 
    {sp: 'tpr', ep: 'erd'}, 
    {sp: 'erd', ep: 'blr'}
];

The output should be ["cbe", "tpr", "erd", "blr"]

what I tried is posted as an answer and it works but I used two maps to get the desired output. I know there should be a way better than my answer.

Here is my code on stackblitz

Benjaco · Accepted Answer · 2018-11-03 18:51:07Z

3

The new flatMap function can be used here, but be aware of limited browser support

trip = [
    {sp: 'cbe', ep: 'tpr'}, 
    {sp: 'tpr', ep: 'erd'}, 
    {sp: 'erd', ep: 'blr'}
];

res = [ ...new Set(   trip.flatMap(Object.values)    )]

console.log(res)

edited Nov 3, 2018 at 18:51

answered Nov 3, 2018 at 18:21

Benjaco

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2 Comments

anonymous Over a year ago

can you tell ,me what flatmap does?

Bergi Over a year ago

@anonymous Just follow the link in the answer!

Jim B. · Accepted Answer · 2018-11-03 19:20:48Z

1

Here's another way: (updated to aggregate all keys instead of explicit keys)

const trip = [
    {sp: 'cbe', ep: 'tpr'}, 
    {sp: 'tpr', ep: 'erd'}, 
    {sp: 'erd', ep: 'blr'}
];

const t = Array.from(trip.reduce((a, el) => {
    for (let key in el) a.add(el[key]);
    return a;
}, new Set()));

console.log(t);

edited Nov 3, 2018 at 19:20

answered Nov 3, 2018 at 18:26

Jim B.

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1 Comment

slider Over a year ago

I don't think you explicitly need to provide an empty array to the Set constructor. Also, the final result here will be a Set not an array. You can fix that with Array.from(trip.reduce...).

anonymous · Accepted Answer · 2018-11-04 07:39:42Z

1

    const trip = [
        {sp: 'cbe', ep: 'tpr'}, 
        {sp: 'tpr', ep: 'erd'}, 
        {sp: 'erd', ep: 'blr'}
    ];
    const r = trip.map( m => {
      return m.sp
    });
    const s = trip.map( m => {
      return m.ep
    });
    console.log(Array.from(new Set(r.concat(s))));

edited Nov 4, 2018 at 7:39

answered Nov 3, 2018 at 18:10

anonymous

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Comments

HynekS · Accepted Answer · 2018-11-03 18:33:12Z

0

If you are O.K. with not-so-much readable one-liner…

trip = [{
    sp: 'cbe',
    ep: 'tpr'
  },
  {
    sp: 'tpr',
    ep: 'erd'
  },
  {
    sp: 'erd',
    ep: 'blr'
  }
];

const res = [...new Set([].concat.apply([], trip.map(item => Object.values(item))))];

console.log(res);

edited Nov 3, 2018 at 18:33

answered Nov 3, 2018 at 18:20

HynekS

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