What does "dispatch()" mean/do, and why is it used when we have .then() and .catch()

Question

I am new to ES6 and advanced javascript. I have seen examples of code using the axios http client like this:

axios.xxx(...).then((res) => dispatch(success(res)) , (err)=> dispatch(error(err)))

whereas I am doing:

axios.xxx(...).then(function(res){...}).catch(function(err){...});

I tried to look up dispatch on MDN but only found DispatchEvent... which is not the same? I ask because although my code works, I am finding http error codes like 403 etc from my api are handled as errors by axios, while i would prefer to handle them myself in the app. (Update: when I added the dispatch tag to this question, I saw a brief summary of the meaning but I am still confused).

What is the reason or advantage for using dispatch? Is "dispatch()" part of axios, or ES6, or nodejs? thx.

Answer 1

When I see dispatch I immediately think of redux-thunk (a popular middleware for Redux). It is a good example of why passing dispatch is useful. Basically dispatch is used as a callback which gets invoked once some async action is complete. In redux-thunk dispatch is simply a function which dispatches an action to the Redux store after, let's say, you fetch data from an API (which is asynchronous). You can pass any function you like to .then() or .catch() of some Promise and it will be invoked upon success or failure.