Axios: how to break promise chain in interceptors?

[Shu-Ji]

How to break promise chain?

instance.interceptors.response.use((response) ->
    # my server returns {"status": "success", "data": ...}
    # or {"status": "fail", "data": ...}
    server_response = response.data
    if server_response.status == 'fail'
        alert(server_response.data)  # global alert when status == 'fail'
        # this will throw a "> Uncaught (in promise) ..."
        # how can i do to prevent/stop it enter into the next then()?
        # only when server_response.status == 'success' enter the `then` function
        return Promise.reject(response)

    # only status == 'success' will reach here:
    return response

# in my button actions
instance
    .post('accounts/login', account)
    .then (response) ->
        # if i don't use Promise.reject() in the interceptors,
        # everytime i will use a if:
        if response.data.status == 'success'
            doThings(response)

        # but i want this
        doThings(response)

in angular:
http://blog.zeit.io/stop-a-promise-chain-without-using-reject-with-angular-s-q/

in bluebird:
http://openmymind.net/Cancelling-Long-Promise-Chains/

the above examples break chains in then(), can axios break it also in interceptor, somthing likes:

instance.interceptors.response.use((response) ->
    if someCondition(response)
        return null  # break the chain
    else
        return response

[rubennorte]

I don't recommend you doing so, but if you finally want it you can return a never-resolving promise in your interceptors. E.g.:

instance.interceptors.response.use((response) => {
  if (someCondition(response) {
    return new Promise(() => {});
  }
  return response;
});

[sccovey]

I didn't like the idea of using a promise that never resolves or rejects, so I opted to use bluebird's cancellation to do something like this:

axios.interceptors.response.use(null, error => {
    let promise = new Promise(resolve, reject) => {
        setTimeout(() => {
            <code>
            promise.cancel()
        })
    })
    return promise
})

the setTimeout allows the promise to initalize itself so that a proper promise is still returned from the interceptor and .cancel() can be called after the fact

[verbart]

Reply to @rubennorte:

I don't recommend you doing so, but if you finally want it you can return a never-resolving promise in your interceptors. E.g.:

instance.interceptors.response.use((response) => {
  if (someCondition(response) {
    return new Promise(() => {});
  }
  return response;
});

https://stackoverflow.com/a/20068922

In short - at least in modern browsers - you don't have to worry about unresolved promises as long as you don't have external references to them