actions.js

// reducer.js
export default function reducer(state=initialState, action) {
  switch(action.type) {
    case defs.MAKE_PAYMENT_SUCCESS:
      return state.withMutations(s =>
        s.set('modalOpen', false)
         .set('loading', false)
         .setIn(['loans', action.loan.id], Immutable.fromJS(action.loan))
      )
    case defs.MAKE_PAYMENT_FAILED:
      return state.withMutations(s =>
        s.set('modalOpen', false)
         .set('loading', false)
         .set('paymentError', action.error)
      )
    // ...
  }
}
// actions.js
export function makePayment(loanId, amount, paymentMethodId) {
  return async dispatch => {
    dispatch(makePaymentSent())
    const response = await api.makePayment(loanId, amount, paymentMethodId)
    if (response.status !== 200) {
      dispatch(makePaymentFailed(response.statusText))
    } else {
      const result = await response.json()
      dispatch(makePaymentSuccess(result.data))
    }
  }
}