newsemitter

node-newsemitter

An event emitter that emits only new events. Because sometimes we don't care about old events.

Usage

const NewsEmitter = require('newsemitter');
const news = new NewsEmitter();

news.on('item', (item) => {
  console.log('new item:', item.title);
});

news.emit('item', { title: 'hello there' });
news.emit('item', { title: 'hello world' });
news.emit('item', { title: 'hello there' });
news.emit('item', { title: 'hey' });
news.emit('item', { title: 'hey' });
news.emit('item', { title: 'hey' });

// new item: hello there
// new item: hello world
// new item: hey

API

new NewsEmitter([options])

Creates an instance of a NewsEmitter. options can be

• filter - An array of events that will be affected. If not given, event names will not be filtered.
• ignore - An array of events that will be ignored. Defaults to ['newListener', 'removeListener'].
• maxHistory - Maximum number of history items to remember. Default is 10.
• manageHistory - If true, does not add emitted events to history. Instead expects you to manually manage history with addHistory(). Defaults to false.
• identifier - Function used to compare one event to another. Called with a list of arguments that NewsEmitter#emit() is called with, sans event name. Should return a string. Default is JSON.stringify.

NewsEmitter#emit(event)

Emits an event, only if it has not been emitted before. Returns true if item is new and emtted. False otherwise.

NewsEmitter#reset([event])

Resets history of an event. If no event given, resets all history.

NewsEmitter#addHistory(event, arr)

Adds items in arr as event's history. Truncated as necessary based on max history length considering the last item in the array as newest.

Install

npm install newsemitter

Tests

Tests are written with mocha

npm test