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; // use esnext if you're only using node 10.x or supporting very new browsers;
Reference Documentation
Examples
fromEvent
fromEvent
turns DOM events into an iterable.
; const clicks = ; for { console;}
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 iterableconst lines = ; // create a filter that removes empty linesconst notEmpty = ; // convert to uppercaseconst toUpperCase = ; // go through each of the non empty linesfor await const line of lines console;
Subject
Subject
makes it easy to turn stream of events into an iterable. The code below
is essentially how fromEvent
was implemented.
; const subject = ; // set up a callback that calls value on the subjectconst callback = subject; // attach the callback to the click eventdocument; // remove the callback when / if the iterable stopssubject; // go through all the click eventsfor { console;}
Avoiding leaks
It's possible to have an async iterator leak if it never returns a value e.g.:
const subject1 = ;const subject2 = ; { try for { i; } finally console } { for awaitconst i of break; } subject1
If you need to be able to cancel async iterators that may never return values, consider Rx or regular Observables for now.
(Thanks to @awto for the example)