The difference between Redux-Logic and Redux-thunk

1. Redux-thunk is very simple (about 10 lines of code) middleware which allows to dispatch functions. That is all it do.

   When dispatching function you can do some other work (inside this function), like fetching data or something else before/after dispatching action (action - means object which will go directly to reducer).

2. Redux-logic is much more flexible and powerful middleware. It allows to express your intention when writing code.

This sample taken from documentation

const fetchPollsLogic = createLogic({

  // declarative built-in functionality wraps your code
  type: FETCH_POLLS, // only apply this logic to this type
  cancelType: CANCEL_FETCH_POLLS, // cancel on this type
  latest: true, // only take latest

  // your code here, hook into one or more of these execution
  // phases: validate, transform, and/or process
  process({ getState, action }, dispatch, done) {
      axios.get('https://survey.codewinds.com/polls')
          .then(resp => resp.data.polls)
          .then(polls => dispatch({ type: FETCH_POLLS_SUCCESS,
                            payload: polls }))
          .catch(err => {
              console.error(err); // log since could be render err
              dispatch({ type: FETCH_POLLS_FAILED, payload: err,
                    error: true })
       })
       .then(() => done()); // call done when finished dispatching
    }
});

This sample is fetching data, but it intention and stages (in this case it has only one stage, process) is clear from code.

Doing the same using Redux-thunk will lead to such code

const fetchPollsLogic = () => (dispatch) => {
    axios.get('https://survey.codewinds.com/polls')
       .then(resp => resp.data.polls)
       .then(polls => dispatch({ type: FETCH_POLLS_SUCCESS,
                            payload: polls }))
       .catch(err => {
           console.error(err); // log since could be render err
           dispatch({ type: FETCH_POLLS_FAILED, payload: err,
                 error: true })
        })
 }

The code is essentially the same, but lacks of declarative style, division into stages and so on.

I may recommend to read thru redux-logic, as it much more powerful and flexible compared to redux-thunk