selectUserObservable.js

import { get } from 'lodash'
import { createEventHandler } from 'recompose'

const selectUser = mapPropsStream(props$ => {
  const { stream: selected$, handler: userSelect } = createEventHandler()
  return props$.pipe(
    switchMap(props => {
      const userInURL = get(props, 'match.params.user')
      return selected$
        .pipe(
          startWith(
            props.userList
              && userInURL
                ? props.userList.find(userInList => userInList.user === userInURL)
                : props.userList[0]
          )
        )
        .pipe(map(selectedUser => ({ ...props, selectedUser, userSelect })))
    })
  )
})