stale-state

A helper library to deal with servers that occasionally return stale data as a response. This can be problematic if you use the server state to update a UI and it switches between old and new state.

Install

The module is released in to the public npm registry and can be installed using:

npm install --save stale-state

API

import StaleState from 'stale-state';
const stale = new StaleState({ /* options here */ });

The following options are accepted:

• previously Allows you to set an initial state.
• name Name of the instance. Used in our debug output.
• requests The amount of requests need to be made to validate if declined data is really out of data.
• interval Interval for the fetch function.

request

Add a function that does the request for data that might need a verification. The supplied function receives a single argument which is an error first completion callback.

stale.request((next) => {
  your.api.call(data, function (err, data) {
    next(err, data);
  });
});

check

This is the most important API in this module, the part where you verify if the received data is stale or not and decline or accept the new data. The supplied method receives 3 arguments:

• previously The previous data that we received.
• currently The new data that we received from your request method.
• state An object with an accept, same and decline function to accept or decline the newly requested data.

stale.check((previous, current, state) => {
  if (previous.value == current.value) return state.same();
  if (previous.value < currrent.value) return state.accept();

  state.decline();
});

fetch

Start fetching data. This calls the request method and starts processing the data using the check method. If an interval is set in the options it will also start a new interval so your data will be fetched continuously if you need to poll a specific endpoint.

stale.fetch();

commit

We've found a new accepted state that can be used in your application. This function receives the newly checked data.

stale.commit((data) => {
  application.setState(data);
});

error

Receives all errors that happen during checking. For example your request method is now calling the callback with errors etc.

stale.error((err) => {
  console.error(err);
});

License

MIT