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

• Tomasz Bubała: Copying data gives me syntax error, can you fix it?
• ukaric: 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.
• Rahul Sharma: name: 'Name2' is inside countries array of Name1 is it correct?
• ukaric: @RahulSharma fixed the original data source my bad.

Answer 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);

• ukaric: 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: 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: Yeah I for sure will :D

Answer 2

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);

Answer 3

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 )