问题
Need a help from Ramda community... I have an object array that I need to sort by "chapter_id" and after sorting, just remove "chapter_id":
const stuff = [
{ id: 1, title: "hello world", chapter_id: "4321" },
{ id: 2, title: "new title", chapter_id: "21" },
{ id: 3, title: "...", chapter_id: "33" },
{ id: 4, title: "huh!?", chapter_id: "14" },
{ id: 5, title: "From Earth", chapter_id: "11" },
{ id: 6, title: "alien", chapter_id: "11" },
{ id: 7, title: "Saturn", chapter_id: "11" },
{ id: 8, title: "Mars:/", chapter_id: "21" },
{ id: 9, title: "damn", chapter_id: "3" },
{ id: 10, title: "test", chapter_id: "11" },
{ id: 11, title: "ramda heeeelp", chapter_id: "31" },
{ id: 12, title: "hello?", chapter_id: "21" }
]
And as result I want to get this object:
{
"3": [
{
"id": "9",
"title": "damn"
}
],
"11": [
{
"id": "5",
"title": "From Earth"
},
{
"id": "6",
"title": "alien"
},
{
"id": "7",
"title": "Saturn"
},
{
"id": "10",
"title": "test"
}
],
"14": [
{
"id": "4",
"title": "huh!?"
}
],
"21": [
{
"id": "2",
"title": "new title"
},
{
"id": "8",
"title": "Mars:/"
},
{
"id": "12",
"title": "hello?"
}
],
"31": [
{
"id": "11",
"title": "ramda heeeelp"
}
],
"33": [
{
"id": "3",
"title": "..."
}
],
"4321": [
{
"id": "1",
"title": "hello world"
}
]
}
How I struggled with this:
let object = {};
map(({ chapter_id }) => {
const composed = compose(
map(evolve({ id: toString })), //here id is converted to a string
filter(c => c.chapter_id === chapter_id),
);
object[chapter_id] = composed(stuff)
}, stuff);
My result:
{
"3": [
{
"id": "9",
"title": "damn",
"chapter_id": "3" //Dissoc this
}
],
"11": [
{
"id": "5",
"title": "From Earth",
"chapter_id": "11" //dissoc this
},
{
"id": "6",
"title": "alien",
"chapter_id": "11" //and this
},
{
"id": "7",
"title": "Saturn",
"chapter_id": "11" //and this
},
{
"id": "10",
"title": "test",
"chapter_id": "11" //and this
}
],
"14": [
{
"id": "4",
"title": "huh!?",
"chapter_id": "14" //and this
}
],
"21": [
{
"id": "2",
"title": "new title",
"chapter_id": "21" //and this
},
{
"id": "8",
"title": "Mars:/",
"chapter_id": "21" //and this
},
{
"id": "12",
"title": "hello?",
"chapter_id": "21" //and this
}
],
"31": [
{
"id": "11",
"title": "ramda heeeelp",
"chapter_id": "31" //and this!!!!!!
}
],
"33": [
{
"id": "3",
"title": "...",
"chapter_id": "33" //and this..
}
],
"4321": [
{
"id": "1",
"title": "hello world",
"chapter_id": "4321" //and this:(
}
]
}It works but I can't dissoc "chapter_id" from each object, does anyone know how to solve this? :Δ
回答1:
As Ori Drori notes, this is the likely Ramda method:
const transform = pipe (
groupBy(prop('chapter_id')),
map(map(dissoc('chapter_id'))),
)
But if you need to actually sort the keys, as your answer suggests, then it will take a bit more processing. You might try something like this:
const transform = pipe (
groupBy(prop('chapter_id')),
map(map(dissoc('chapter_id'))),
toPairs,
sortBy(pipe(head, Number)),
fromPairs
)
const stuff = [{id: 1, title: "hello world", chapter_id: "4321"}, {id: 2, title: "new title", chapter_id: "21"}, {id: 3, title: "...", chapter_id: "33"}, {id: 4, title: "huh!?", chapter_id: "14"}, {id: 5, title: "From Earth", chapter_id: "11"}, {id: 6, title: "alien", chapter_id: "11"}, {id: 7, title: "Saturn", chapter_id: "11"}, {id: 8, title: "Mars: /", chapter_id: "21"}, {id: 9, title: "damn", chapter_id: "3"}, {id: 10, title: "test", chapter_id: "11"}, {id: 11, title: "ramda heeeelp", chapter_id: "31"}, {id: 12, title: "hello?", chapter_id: "21"}]
console.log (
transform (stuff)
)<script src="//cdnjs.cloudflare.com/ajax/libs/ramda/0.26.1/ramda.js"></script>
<script> const {pipe, groupBy, prop, map, dissoc, toPairs, sortBy, head, fromPairs} = R </script>That sorting line could be written in many ways. Perhaps
sort(lift(subtract)(head, head)),
or just
sort(([a], [b]) => a - b),
And obviously if you were so inclined, you could pull out a sortByKeys function like this:
const sortByKeys = (fn) => pipe(toPairs, sortBy(fn), fromPairs)
sortByKeys is not a likely candidate for inclusion in Ramda, which really prefers to think of objects as unordered collections of name-value pairs. But it could easily go in your own helper library.
回答2:
With Ramda you can group by the key, and then map the groups, and dissoc the key from all objects:
const { pipe, groupBy, prop, map, dissoc } = R;
const fn = key => pipe(
groupBy(prop(key)), // group by the key
map(map(dissoc(key))) // remove the key from all objects in all groups
);
const stuff = [{"id":1,"title":"hello world","chapter_id":"4321"},{"id":2,"title":"new title","chapter_id":"21"},{"id":3,"title":"...","chapter_id":"33"},{"id":4,"title":"huh!?","chapter_id":"14"},{"id":5,"title":"From Earth","chapter_id":"11"},{"id":6,"title":"alien","chapter_id":"11"},{"id":7,"title":"Saturn","chapter_id":"11"},{"id":8,"title":"Mars:/","chapter_id":"21"},{"id":9,"title":"damn","chapter_id":"3"},{"id":10,"title":"test","chapter_id":"11"},{"id":11,"title":"ramda heeeelp","chapter_id":"31"},{"id":12,"title":"hello?","chapter_id":"21"}];
const result = fn('chapter_id')(stuff);
console.log(result);<script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.26.1/ramda.js"></script>回答3:
First of all the finite task is not properly described :) What you really want (based on the result I want to get section) is to normalize (or restructure) the array of objects into an object, which have the chapter_id as a key, and the value is an array of the associated records of the stuff array with that chapter_id
On my opinion, your solution is cool and seems like a more functional, but in this particular case I've probably will give a preference to the simple reduce function, which is more readable...
reduce((acc, {chapter_id, ...rest}) => {
const isInitialized = !!acc[chapter_id];
if (isInitialized) {
acc[chapter_id].push(rest);
} else {
acc[chapter_id] = [rest];
}
return acc;
}, {}, stuff);
来源：https://stackoverflow.com/questions/58682137/group-arrays-by-parent-ids-object-ramda