data-poller

Data Poller

Poller is an abstraction that can be used to add polling to any data module that uses the following conventions:

• The module emits change events when data changes and expects consumers to bind to the change event to be notified when a change occurs
• Has a method or public function that can be called to initiate an AJAX request for new data
• Uses the EventEmitter or a derivative to emit the change event
• The data module is a single object instance that is used throughout

The module works by initiating polling when the data module has one or more objects listening for a change and stopping when there are no longer any change events bound. Polling is also paused when the visibility state of the page changes to hidden and resumed when the page is focused, unless the pauseWhenHidden option is set to false.

Usage

Pollers#add( store, method, [options] )

Add a new poller that fetches updates

• @param {object} store - instance of a data store, typically a singleton
• @param {string} method - method of the store that will be called to update the store
• @param {object} [options] - optional set of options passed to the Poller constructor
  • interval - time in ms between each call to the fetch method (default: 30000)
  • leading - whether or not fetch is called when starting the Poller when the instance is created (default: true)
    • pauseWhenHidden - whether or not to pause this poller when the browser tab is hidden

Pollers#remove( poller )

• @param {int|object} poller - id or instance of the poller to remove

Example

import PollerPool from 'calypso/lib/data-poller';
import SitesList from 'calypso/lib/sites-list/list';

const sites = new SitesList();

// 'interval' is the time between polling requests and 'leading' is a flag that controls whether the `fetch` method
// is called when the poller is started when it is added
const poller = PollerPool.add( sites, 'fetch', { interval: 60000, leading: true } );

// remove instance from pool
PollerPool.remove( poller );