Create a new array of objects by property value from existing object add existing objects to new arr-CodePudding

I have an existing array of objects which share a property titled type like so

[
 {
   id: 1,
   name: 'a',
   type: 'foo',
 },{
   id: 2,
   name: 'b',
   type: 'bar',
 },{
   id: 3,
   name: 'c',
   type: 'fizz',
 },{
   id: 4,
   name: 'd',
   type: 'foo',
 },
]

I need to be able to structure a new array of objects with the existing ones grouped together by type like this

[
 {
  type: 'foo',
  groups: [
    {
      id: 1,
      name: 'a',
      type: 'foo',
    },{
      id: 4,
      name: 'd',
      type: 'foo',
    },
  ]
 },{
  type: 'bar',
  groups: [
    {
      id: 2,
      name: 'b',
      type: 'bar',
    }
  ]
 },{
  type: 'fizz',
  groups: [
    {
      id: 3,
      name: 'c',
      type: 'fizz',
    }
  ]
 }
]

this is what I have so far but im not able to create the new array and organize the objects by type, only able to grab the type itself any help would be greatly appreciated!

Observable.value.map(objects => {
    typesArr = [...new Set(objects.data.map(object => object.type))];
}); /// output = ['foo', 'bar', 'fizz']

CodePudding user response：

Reduce the array to a Map, using the type as the key. Use Array.from() to convert the Map's values iterator to an array:

const arr = [{"id":1,"name":"a","type":"foo"},{"id":2,"name":"b","type":"bar"},{"id":3,"name":"c","type":"fizz"},{"id":4,"name":"d","type":"foo"}]

const result = Array.from(arr.reduce((acc, o) => {
  const type = o.type
  if(!acc.has(type)) acc.set(type, { type, groups: [] })
  
  acc.get(type).groups.push(o)
  
  return acc
}, new Map()).values())

console.log(result)

To make TS infer the type of the grouped array, infer the type of an item from the original array, and use it to set the type of the Map (TS playground):

const arr = [{"id":1,"name":"a","type":"foo"},{"id":2,"name":"b","type":"bar"},{"id":3,"name":"c","type":"fizz"},{"id":4,"name":"d","type":"foo"}]

type Item = (typeof arr)[0]

const result = Array.from(arr.reduce((acc, o) => {
  const type = o.type
  if(!acc.has(type)) acc.set(type, { type, groups: [] })
  
  acc.get(type)!.groups.push(o)
  
  return acc
}, new Map<string, { type: Item['type'], groups: Item[] }>()).values())

console.log(result)