How can i make two objects out of one object, dividing them by a value in the object with lodash - arrays

Question

Consider this object, with two channels with NL language and one with EN language:
[
{
"name": "De Redactie",
"channels": [
{
"name": "headlines",
"pubDate": "2017-05-15 09:15:00",
"language": "nl",
"items": [
]
},
{
"name": "headlines English",
"pubDate": "2017-05-14 18:05:00",
"language": "en",
"items": [
]
},
{
"name": "politiek",
"pubDate": "2017-05-14 20:11:00",
"language": "nl",
"items": [
]
}
]
}
]
How can i divide them so that i can get this result:
[
{
"name": "De Redactie",
"channels": [
{
"name": "headlines",
"pubDate": "2017-05-15 09:15:00",
"language": "nl",
"items": [
]
},
{
"name": "politiek",
"pubDate": "2017-05-14 20:11:00",
"language": "nl",
"items": [
]
}
]
}
{
"name": "De Redactie",
"channels": [
{
"name": "headlines English",
"pubDate": "2017-05-14 18:05:00",
"language": "en",
"items": [
]
}
]
}
]
Mind you that this is dummyData. The actual data can contain x amount of one language and y amount of the second or third or fourth ...
I have tried looking in the lodash documentation for the correct combination of functions. Also tried various complex forEach structures, but could not wrap my head around it.
Preferably a solution with lodash or typescript, as i'm working in Angular 4.

Answer 1

Iterate the array with Array#map. For each object, extract the array of channels using destructuring with object rest. Iterate the channels using Array#reduce and group channels with the same language to a Map. Convert back to an array by spreading the Map's values iterator.
Create an array of objects, by mapping them and assigning the group as the channels prop of the object. Flatten the array by spreading into Array#concat:
const data = [{"name":"De Redactie","channels":[{"name":"headlines","pubDate":"2017-05-15 09:15:00","language":"nl","items":[]},{"name":"headlines English","pubDate":"2017-05-14 18:05:00","language":"en","items":[]},{"name":"politiek","pubDate":"2017-05-14 20:11:00","language":"nl","items":[]}]}];
const result = [].concat(...data.map(({ channels, ...rest }) => {
const channelGroups = [...channels.reduce((m, channel) => {
m.has(channel.language) || m.set(channel.language, []);
m.get(channel.language).push(channel);
return m;
}, new Map()).values()];
return channelGroups.map((channels) => ({
...rest,
channels
}));
}));
console.log(result);

Answer 2

way with lodash:
const res = _.chain(arr)
.flatMap(item => _.map( // get array of channels with parent name
item.channels,
channel => _.assign({}, channel, { parentName: item.name })
))
.groupBy('language') // group channels by language
.values() // get channel arrays for each lang
.map(langArrs => ({ // set finished structure
name: _.first(langArrs).parentName, // get name for lang channels
channels: _.omit(langArrs, ['parentName']) // set channels without parent name
}))
.value();