groupBy

연산자(operator) 정의: groupBy(keySelector: Function, elementSelector: Function): Observable

Group into observables based on provided value.

Examples

Example 1: Group by property

( jsBin | jsFiddle )

const people = [{name: 'Sue', age:25},{name: 'Joe', age: 30},{name: 'Frank', age: 25}, {name: 'Sarah', age: 35}];
//emit each person
const source = Rx.Observable.from(people);
//group by age
const example = source
  .groupBy(person => person.age)
  //return as array of each group
  .flatMap(group => group.reduce((acc, curr) => [...acc, curr], []))
/*
  output:
  [{age: 25, name: "Sue"},{age: 25, name: "Frank"}]
  [{age: 30, name: "Joe"}]
  [{age: 35, name: "Sarah"}]
*/
const subscribe = example.subscribe(val => console.log(val));

Additional Resources

• groupBy - Official docs
• Group higher order observables with RxJS groupBy - André Staltz
• Use groupBy in real RxJS applications - André Staltz

Source Code: https://github.com/ReactiveX/rxjs/blob/master/src/operator/groupBy.ts