CODEWITHSUNDEEP
angularrxjsangular2-observables
Lucifer
Lucifer

Reputation: 2357

RxJs groupBy with an array of objects each having key and values array

So the requirement is like: I got a array of objects (e.g. Array)

[
   { empDept: 'Engineering', empLoc: 'Pune', empName: 'John' },
   { empDept: 'Engineering', empLoc: 'Mumbai', empName: 'Harry' },
   { empDept: 'HR', empLoc: 'Pune', empName: 'Denis' },
   { empDept: 'Finance', empLoc: 'Mumbai', empName: 'Elvis' },
]

I will have a function which will accept the name of the property as a parameter, on which the employee list will be grouped. So if the input parameter value is 'empDept', then I want the result as below:

[
   {
      key: 'Engineering',
      values: [
         { empDept: 'Engineering', empLoc: 'Pune', empName: 'John' },
         { empDept: 'Engineering', empLoc: 'Mumbai', empName: 'Harry' },
     ]
   },
   {
      key: 'HR',
      values: [
         { empDept: 'HR', empLoc: 'Pune', empName: 'Denis' },
     ]
   },
   {
      key: 'Finance',
      values: [
        { empDept: 'Finance', empLoc: 'Mumbai', empName: 'Elvis' },
     ]
   }
]

I'm using the RxJs groupBy operator to achieve this. I have tried the below code, but it doesn't seem to give the desired result:

this.groupedEmployees$ = employees$.pipe(
      groupBy(person => person.empDept),
      mergeMap(group => of({ key: group.key, values: group.pipe(mergeMap(x => toArray())) })),
    );

Appreciate your help.

Upvotes: 3

Views: 7710

Answers (3)

Mladen
Mladen

Reputation: 2210

If you really want to stick with RxJS, you can use this piece of code:

import { from } from 'rxjs'; 
import { groupBy, mergeMap, reduce, toArray } from 'rxjs/operators';

const groupedEmployees$ = from([
  { empDept: 'Engineering', empLoc: 'Pune', empName: 'John' },
  { empDept: 'Engineering', empLoc: 'Mumbai', empName: 'Harry' },
  { empDept: 'HR', empLoc: 'Pune', empName: 'Denis' },
  { empDept: 'Finance', empLoc: 'Mumbai', empName: 'Elvis' }
]).pipe(
  groupBy(person => person.empDept),
  mergeMap(group => group
    .pipe(
      reduce((acc, cur) => {
          acc.values.push(cur);
          return acc;
        },
        { key: group.key, values: [] }
      )
    )
  ),
  toArray()
);

groupedEmployees$.subscribe(console.log);

Upvotes: 9

Damian Plewa
Damian Plewa

Reputation: 1193

Are you looking for something like this?

function groupBy(key, array) {
  return array.reduce((all, current) => {
    const existingKey = all.find(existing => existing.key === current[key]);
    if (!existingKey) {
      all.push({key: current[key], values: [current]});
    } else {
      existingKey.values.push(current);
    }
    return all;
  }, []);
}

Example:

const arr = [
   { empDept: 'Engineering', empLoc: 'Pune', empName: 'John' },
   { empDept: 'Engineering', empLoc: 'Mumbai', empName: 'Harry' },
   { empDept: 'HR', empLoc: 'Pune', empName: 'Denis' },
   { empDept: 'Finance', empLoc: 'Mumbai', empName: 'Elvis' },
];

const byDept = groupBy('empDept', arr);
const byLoc = groupBy('empLoc', arr);

Upvotes: 0

HTN
HTN

Reputation: 3604

Why would you use rxjs in this case? It's purely array transformation. You can use lodash groupBy: https://lodash.com/docs/#groupBy


const t = [
   { empDept: 'Engineering', empLoc: 'Pune', empName: 'John' },
   { empDept: 'Engineering', empLoc: 'Mumbai', empName: 'Harry' },
   { empDept: 'HR', empLoc: 'Pune', empName: 'Denis' },
   { empDept: 'Finance', empLoc: 'Mumbai', empName: 'Elvis' },
];

const result = Object.entries(_.groupBy(t, 'empDept')).map(([key, values]) => ({key, values}));

Upvotes: 0

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