Transform nested array of objects

Question

Given the input array.

  let data = [
    {
      name: 'Name',
      countries: [
        {
          name: 'Country1',
          competitions: [
            {
              name: 'Competition1',
              matches: [
                { details: 'details' },
                { details: 'details' },
                { details: 'details' }
              ]
            },
            {
              name: 'Competition2',
              matches: [{ details: 'details' }]
            }
          ]
        },
        {
          name: 'Country2',
          competitions: [
            {
              name: 'Competition1',
              matches: [{ details: 'details' }]
            },
            {
              name: 'Competition2',
              matches: [{ details: 'details' }]
            },

            {
              name: 'Competition3',
              matches: [{ details: 'details' }, { detals: 'detail' }]
            }
          ]
        }
      ]
    },
    {
      name: 'Name2',
      countries: [
        {
          name: 'Country1',
          competitions: [
            {
              name: 'Competition1',
              matches: [{ details: 'details' }, { details: 'details' }]
            }
          ]
        }
      ]
    }
  ];

And desired output:

let sorted = [
    // For each Object in orginal array extract all matches and put it in new array.
    { name: 'Name', matches: [{}, {}, {}, {}, {}, {}, {}, {}] },
    { name: 'Name2', matches: [{}, {}] }
  ]

How can I transform data into sorted I can use nested 3 nested for loops and extract all matches into single array. But it does not give me desired output and I feel that nesting for loops is bad for resources and I'm certain that it can be done more concisely and after all I do not get expected output. I tried Object.assign creating new objects at starts etc etc.

Using for loop to get arr to store all matches from whole data array like so.

  for (var i = 0; i < data.length; i++) {
    for (var j = 0; j < data[i].countries.length; j++) {
      for (var l = 0; l < data[i].countries[j].competitions.length; l++) {
        for (
          var k = 0;
          k < data[i].countries[j].competitions[l].matches.length;
          k++
        ) {
          arr.push(data[i].countries[j].competitions[l].matches[k]);
        }
      }
    }

Is eyesore, and still leaves me with flat array of all matches which are no good.

Using ES6 and new goodies I manage to get closer to solution but leaves me with nested array of arrays that I can not seem to flatten.

  const d = data.map(i => {
    const inter = i.countries.map(e => e.competitions.map(z => z.matches));

    const final = inter.reduce((acc, next) => [...acc, ...next], []);

    return {
      name: i.name,
      matches: final
    };
  })

For educational purposes all solutions will be accepted no matter the performance at this point.

tl;dr How to transform data into sorted

I shortened the next entry in array for readability. Just copy first item in array once more instead of second entry. Or better yet i will add another entry. — ukaric
– ukaric, Commented Mar 9, 2018 at 10:16
name: 'Name2' is inside countries array of Name1 is it correct? — Rahul Sharma
– Rahul Sharma, Commented Mar 9, 2018 at 10:17

Tomasz Bubała · Accepted Answer · 2018-03-09 10:38:46Z

1

const sorted = data.map(o => {
  const name = o.name;
  let matches = [];
  o.countries.map(c => {
    return c.competitions.forEach(c => {
      c.matches.forEach(m => {
        matches.push(m);
      });
    });
  });
  return { name, matches };
});

Instead of using map, I created matches array, and while looping through every matches array from object, I'm just pushing the results into array. Here's a snippet:

let data = [
    {
      name: 'Name',
      countries: [
        {
          name: 'Country1',
          competitions: [
            {
              name: 'Competition1',
              matches: [
                { details: 'details' },
                { details: 'details' },
                { details: 'details' }
              ]
            },
            {
              name: 'Competition2',
              matches: [{ details: 'details' }]
            }
          ]
        },
        {
          name: 'Country2',
          competitions: [
            {
              name: 'Competition1',
              matches: [{ details: 'details' }]
            },
            {
              name: 'Competition2',
              matches: [{ details: 'details' }]
            },

            {
              name: 'Competition3',
              matches: [{ details: 'details' }, { detals: 'detail' }]
            }
          ]
        }
      ]
    }
  ];
const sorted = data.map(o => {
  const name = o.name;
  let matches = [];
  o.countries.map(c => {
    return c.competitions.forEach(c => {
      c.matches.forEach(m => {
        matches.push(m);
      });
    });
  });
  return { name, matches };
});
console.log(sorted);

edited Mar 9, 2018 at 10:38

answered Mar 9, 2018 at 10:33

Tomasz Bubała

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3 Comments

ukaric Over a year ago

Thanks I ended up with this one, because it does not use concat. Did not even cross my mind for a second to break out of map like that. You learn everyday.

Tomasz Bubała Over a year ago

I tried answering with map and then i remembered i had this problem once and came up with forEach and pushing into array. Next time you will remember it too, i guarantee! :)

ukaric Over a year ago

Yeah I for sure will :D

Eddie · Accepted Answer · 2018-03-09 10:30:39Z

You can to use reduce and just concat the matches

let result = data.map(v=>{
    let inter = v.countries.reduce((c,v)=> c.concat( v.competitions.map(z => z.matches).reduce((x,z) => x.concat( z ),[] ) ),[]);
    return {
        name : v.name,
        matches : inter
    }
});

Here is a snippet:

let data = [{
    name: 'Name',
    countries: [{
        name: 'Country1',
        competitions: [{
            name: 'Competition1',
            matches: [{
                details: 'details'
              },
              {
                details: 'details'
              },
              {
                details: 'details'
              }
            ]
          },
          {
            name: 'Competition2',
            matches: [{
              details: 'details'
            }]
          }
        ]
      },
      {
        name: 'Country2',
        competitions: [{
            name: 'Competition1',
            matches: [{
              details: 'details'
            }]
          },
          {
            name: 'Competition2',
            matches: [{
              details: 'details'
            }]
          },

          {
            name: 'Competition3',
            matches: [{
              details: 'details'
            }, {
              detals: 'detail'
            }]
          }
        ]
      },
    ]
  },
  {
    name: 'Name2',
    countries: [{
      name: 'Country1',
      competitions: [{
          name: 'Competition1',
          matches: [{
              details: 'details'
            },
            {
              details: 'details'
            },
            {
              details: 'details'
            }
          ]
        },
        {
          name: 'Competition2',
          matches: [{
            details: 'details'
          }]
        }
      ]
    }, ]
  }
];

let result = data.map(v => {
  let inter = v.countries.reduce((c, v) => c.concat(v.competitions.map(z => z.matches).reduce((x, z) => x.concat(z), [])), []);
  return {
    name: v.name,
    matches: inter
  }
});

console.log(result);

Slai · Accepted Answer · 2018-03-09 23:12:15Z

Might be easier to filter during parsing:

let sorted = [], last = [], json = '[{"name":"Name","countries":[{"name":"Country1","competitions":[{"name":"Competition1","matches":[{"details":"details1"},{"details":"details2"},{"details":"details3"}]},{"name":"Competition2","matches":[{"details":"details4"}]}]},{"name":"Country2","competitions":[{"name":"Competition1","matches":[{"details":"details5"}]},{"name":"Competition2","matches":[{"details":"details6"}]},{"name":"Competition3","matches":[{"details":"details7"},{"detals":"detail8"}]}]}]},{"name":"Name2","countries":[{"name":"Country1","competitions":[{"name":"Competition1","matches":[{"details":"details9"},{"details":"details10"}]}]}]}]'

JSON.parse(json, (k, v) => k === 'details' ? last.push(v) : 
  v.countries !== void 0 ? (sorted.push({ name: v.name, matches: last }), last = []) : 0)

console.log( sorted )

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