Return array of names from array of objects

Question

I know how to loop through an object and print out an array of values I want, but I'm having trouble figuring out printing it in the order that I want .

**The question is: **

Given a collection of game outcome records, determine who all the players are by returning an array of their names.

The array should be ordered by how the names are encountered.

Example Input:

[
  { winner: 'Alishah', loser: 'Bob',    loser_points: 3 },
  { winner: 'Maria',   loser: 'Xu Jin', loser_points: 1 },
  { winner: 'Elise',   loser: 'Bob',    loser_points: 2 },
  { winner: 'Elise',   loser: 'Maria',  loser_points: 4 },
  { winner: 'Alishah', loser: 'Maria',  loser_points: 2 },
  { winner: 'Maria',   loser: 'Xu Jin', loser_points: 3 },
  { winner: 'Xu Jin',  loser: 'Elise',  loser_points: 2 }
]

Expected Result:

['Alishah', 'Bob', 'Maria', 'Xu Jin', 'Elise']

**The code I have so far: **

let data = [
  { winner: 'Alishah', loser: 'Bob',    loser_points: 3 },
  { winner: 'Maria',   loser: 'Xu Jin', loser_points: 1 },
  { winner: 'Elise',   loser: 'Bob',    loser_points: 2 },
  { winner: 'Elise',   loser: 'Maria',  loser_points: 4 },
  { winner: 'Alishah', loser: 'Maria',  loser_points: 2 },
  { winner: 'Maria',   loser: 'Xu Jin', loser_points: 3 },
  { winner: 'Xu Jin',  loser: 'Elise',  loser_points: 2 }
];

   
console.log(main(data));

palaѕн · Accepted Answer · 2020-03-27 14:54:46Z

4

You can use .flatMap() and Set() for this:

let data = [
  { winner: 'Alishah', loser: 'Bob',    loser_points: 3 },
  { winner: 'Maria',   loser: 'Xu Jin', loser_points: 1 },
  { winner: 'Elise',   loser: 'Bob',    loser_points: 2 },
  { winner: 'Elise',   loser: 'Maria',  loser_points: 4 },
  { winner: 'Alishah', loser: 'Maria',  loser_points: 2 },
  { winner: 'Maria',   loser: 'Xu Jin', loser_points: 3 },
  { winner: 'Xu Jin',  loser: 'Elise',  loser_points: 2 }
];

const res = [...new Set(data.flatMap(x=>[x.winner, x.loser]))]
console.log( res )

Explanation:

Using .flatMap() method we will first get an array of arrays. Here the inner array will be array of winner & loser names.
Then we will flatten the array to get a single array of all player's name.
And finally using [...new Set(array)] we will get distinct names in the array to achieve the desired result.

edited Mar 27, 2020 at 14:54

answered Mar 27, 2020 at 14:49

palaѕн

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Comments

Harun Yilmaz · Accepted Answer · 2020-03-27 14:49:35Z

You can use Array.reduce() and Set to get names and remove duplicates

Array.reduce() iterates over the array. So you can push all winners and losers to the initial empty array.

Then you can create a new Set. This way, you can remove duplicates (since all items are string). After that, you can convert it back to array by using the spread syntax: [...new Set(array)]

const arr = [
  { winner: 'Alishah', loser: 'Bob',    loser_points: 3 },
  { winner: 'Maria',   loser: 'Xu Jin', loser_points: 1 },
  { winner: 'Elise',   loser: 'Bob',    loser_points: 2 },
  { winner: 'Elise',   loser: 'Maria',  loser_points: 4 },
  { winner: 'Alishah', loser: 'Maria',  loser_points: 2 },
  { winner: 'Maria',   loser: 'Xu Jin', loser_points: 3 },
  { winner: 'Xu Jin',  loser: 'Elise',  loser_points: 2 }
]

const names = [...new Set(arr.reduce((acc, cur) => [...acc, cur.winner, cur.loser], []))]

console.log(names)

Danko · Accepted Answer · 2020-03-27 14:49:44Z

0

var players = collection.reduce((acc, player) => {
    if(!acc.inStore[player.winner]) {
        acc.players.push(player.winner)
        acc.inStore[player.winner] = true
    }
    if(!acc.inStore[player.loser]) {
        acc.players.push(player.loser)
        acc.inStore[player.loser] = true
    }
    return acc;
}, {players: [], inStore: {}}).players

// ["Alishah", "Bob", "Maria", "Xu Jin", "Elise"]

answered Mar 27, 2020 at 14:49

Danko

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Comments

yunzen · Accepted Answer · 2020-03-27 14:56:40Z

0

Use reduce and includes

console.clear();

"use strict";

const score = [
  { winner: 'Alishah', loser: 'Bob',    loser_points: 3 },
  { winner: 'Maria',   loser: 'Xu Jin', loser_points: 1 },
  { winner: 'Elise',   loser: 'Bob',    loser_points: 2 },
  { winner: 'Elise',   loser: 'Maria',  loser_points: 4 },
  { winner: 'Alishah', loser: 'Maria',  loser_points: 2 },
  { winner: 'Maria',   loser: 'Xu Jin', loser_points: 3 },
  { winner: 'Xu Jin',  loser: 'Elise',  loser_points: 2 }
]

function reduce(coll, {winner, loser}) {
  if (!coll.includes(winner)) {
    coll.push(winner)
  }
  if (!coll.includes(loser)) {
    coll.push(loser)
  }
  return coll;
}

var players = score.reduce(reduce, [])
console.log(players)

edited Mar 27, 2020 at 14:56

answered Mar 27, 2020 at 14:43

yunzen

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1 Comment

palaѕн Over a year ago

This is not matching the expected result OP has shared: ['Alishah', 'Bob', 'Maria', 'Xu Jin', 'Elise']

Raffaele · Accepted Answer · 2020-03-27 15:03:15Z

0

Looking your code and your expected result I think you're missing to push into arr also the looser name. To fix it my favourite approach is the reduce method of js array:

const arr = outcomes.reduce((completeList,{winner, looser}) => {
    const extraNames = [winner, looser]
        .filter(x => !completeList.includes(x));
    return [
        ...completeList,
        ...extraNames
    ];
}, []);

edited Mar 27, 2020 at 15:03

answered Mar 27, 2020 at 14:44

Raffaele

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1 Comment

VLAZ Over a year ago

This produces duplicates, each name should only show up once.

A. Khaled · Accepted Answer · 2020-03-29 08:55:21Z

0

Using map and filter

let array = [
  { winner: 'Alishah', loser: 'Bob',    loser_points: 3 },
  { winner: 'Maria',   loser: 'Xu Jin', loser_points: 1 },
  { winner: 'Elise',   loser: 'Bob',    loser_points: 2 },
  { winner: 'Elise',   loser: 'Maria',  loser_points: 4 },
  { winner: 'Alishah', loser: 'Maria',  loser_points: 2 },
  { winner: 'Maria',   loser: 'Xu Jin', loser_points: 3 },
  { winner: 'Xu Jin',  loser: 'Elise',  loser_points: 2 }
];

let winners = array.map(i => i.winner).filter((x, i, a) => a.indexOf(x) == i)
console.log(winners);

answered Mar 29, 2020 at 8:55

A. Khaled

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Comments

tedian_dev · Accepted Answer · 2020-03-27 14:49:58Z

-1

const outcomes = [
  { winner: 'Alishah', loser: 'Bob',    loser_points: 3 },
  { winner: 'Maria',   loser: 'Xu Jin', loser_points: 1 },
  { winner: 'Elise',   loser: 'Bob',    loser_points: 2 },
  { winner: 'Elise',   loser: 'Maria',  loser_points: 4 },
  { winner: 'Alishah', loser: 'Maria',  loser_points: 2 },
  { winner: 'Maria',   loser: 'Xu Jin', loser_points: 3 },
  { winner: 'Xu Jin',  loser: 'Elise',  loser_points: 2 }
];

const result = outcomes.reduce((acc, cur) => {
  if(!acc.includes(cur.winner))
  acc.push(cur.winner);
  if(!acc.includes(cur.loser))
  acc.push(cur.loser);
  return acc;
}, []).join(",");

console.log(result);

edited Mar 27, 2020 at 14:49

answered Mar 27, 2020 at 14:43

tedian_dev

544 bronze badges

2 Comments

palaѕн Over a year ago

This is also not matching the expected result OP has shared: ['Alishah', 'Bob', 'Maria', 'Xu Jin', 'Elise']

tedian_dev Over a year ago

@palaѕн Good catch.

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