Axax – Async iterator extensions for JavaScript
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Async Iterator Extensions
A library of async iterator extensions for JavaScript including map
, reduce
, filter
, flatMap
, pipe
and more
.
Installation
npm install axax # or yarn add axax
Why Axax?
Async iterators are a useful way to handle asynchronous streams. This library adds a number of utility methods similar to those found in lodash, underscore, Ramda or RxJs.
es5 vs esnext
Axax contains both transpiled es5 code as well as esnext code, the difference being that
esnext uses the native for await
syntax. In nodejs 10.x that gives approximately a 40% speedup.
// use es5 if you want to support more browsers import { map } from "axax/es5/map"; // use esnext if you're only using node 10.x or supporting very new browsers import { map } from "axax/esnext/map";
Reference Documentation
Examples
fromEvent
fromEvent
turns DOM events into an iterable.
import { fromEvent } from "axax/es5/fromEvent"; const clicks = fromEvent(document, 'click'); for await (const click of clicks) { console.log('a button was clicked'); }
pipe, map, filter, fromLineReader
fromLineReader
turns a NodeJS LineReader into an async iterable.
The example below prints the lines from a file in upper case after
filtering out the empty ones.
// create the line reading async iterable const lines = fromLineReader( require("readline").createInterface({ input: require("fs").createReadStream("./data/example.txt") }) ); // create a filter that removes empty lines const notEmpty = filter(line => line.length > 0); // convert to uppercase const toUpperCase = map(line => line.toUpperCase()); // go through each of the non empty lines for await (const line of pipe(notEmpty, toUpperCase)(lines)) { console.log(line); }
Subject
Subject
makes it easy to turn stream of events into an iterable. The code below
is essentially how fromEvent
was implemented.
import { Subject } from "axax/es5/subject"; const subject = new Subject(); // set up a callback that calls value on the subject const callback = value => subject.onNext(value); // attach the callback to the click event document.addEventListener('click', callback); // remove the callback when / if the iterable stops subject.finally(() => document.removeEventListener('click', callback)); // go through all the click events for await (const click of subject.iterator) { console.log('a button was clicked'); }
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