Rx combine as object

combine.js

const combineObject = config => {

  const streams = _.values(config)
  const keys = _.keys(config)

  return Rx.Observable.combineLatest(
    ...streams,
    (...values) => _.zip(values, keys).reduce((acc, [value, key]) => {
      acc[key] = value
      return acc
    }, {})
  )
}

const withLatestFromObject = (s$, property, config) => {

  const streams = _.values(config)
  const keys = _.keys(config)

  return s$.withLatestFrom(
    ...streams,
    (s, ...values) => _.zip(values, keys).reduce((acc, [value, key]) => {
      acc[key] = value
      return acc
    }, {
      [property]: s
    })
  )
}

// Usage
const a$ = Rx.Observable.just(1)
const b$ = Rx.Observable.just(2)

combineObject({
  a: a$,
  b: b$
})
.subscribe(c => console.log(c))

// {a: 1, b: 2}

withLatestFromObject(a$, 'a', {
  b: b$
})
.subscribe(c => console.log(c))
// {a: 1, b: 2}