poller-bear v0.2.2

Poller Bear

A simple poller that can be used in both JavaScript and TypeScript projects. With "Poller Bear" you can continuously perform an operation indefinitely or until a condition is met.

Usage

Infinite polling

Polling can be achieved with the Poller class. The most basic initialisation can be achieved by passing a config object containing the function that needs to be executed by the poller. With this basic configuration, the Poller.poll() can be called to infinitely execute the provided function.

import Poller from "poller-bear";

const config = { fn: () => console.log('Polling...') }
const poller = new Poller(config);

await poller.poll();

The implementation above is just a simple demonstration. We wouldn't advise to implement it this way since it would block the rest of your application.

Interval

By default, the poller will poll continuously with no pause. Usually you want to wait a little between each poll. Poller bear allow you to define this via the interval configuration. The code below will poll every 3 seconds.

import Poller from "poller-bear";

const fn = () => console.log('Polling...')
const interval = { ms: 3000 }

const config = { fn, interval }
const poller = new Poller(config);

await poller.poll();

Stop polling on custom condition

In some cases you may wish to poll until a certain condition is met. For example, you may want to poll until an api responds with a certain status. This can be achieved by providing a function to the continuePolling field of our Poller config object

import Poller from 'poller-bear';

const fn = async () => ApiService.get();
const continuePolling = (apiResponse) => apiResponse.status !== 'SUCCESS'

const config = { fn, continuePolling }
const poller = new Poller(config);

const response = await poller.poll();

Once continuePolling returns true, the poller will stop polling and will return the result of your target function.

Max retries

Polling Bear also allows you to define a maximum number of retries. The code below defines a poller that will poll maximum 5 times by setting the maxRetries field to 5. If the limit is reached, a MAX_RETRIES_ERROR error is thrown. The error object can be imported in order to do a check when catching an error.

import Poller, {MAX_RETRIES_ERROR} from 'poller-bear';

try {
    const fn = () => console.log('Polling...');
    const poller = new Poller({ fn, maxRetries: 5 });
    await poller.poll();
} catch(e) {
    if (e === MAX_RETRIES_ERROR) {
        console.error('The poller has reached the max amount of retries')
    } else {
        console.error(e)
    }
}

Timeout

You can also define a maximum amount of time that poller bear should be polling for. This can be done via the timeout object. Once the defined time has elapsed, a TIMEOUT_ERROR error is thrown. Similarly to max retries, the TIMEOUT error can be imported.

import Poller, {TIMEOUT_ERROR} from 'poller-bear';

try {
    const fn = () => console.log('Polling...');
    const poller = new Poller({ fn, timeout: { seconds: 25 } });
    await poller.poll();
} catch(e) {
    if (e === TIMEOUT_ERROR) {
        console.error('The poller has timed out')
    } else {
        console.error(e)
    }
}