Simple Timer Stream

Heads Up: Moved!

This project was integrated into my rx_webstreams library!
Since this project is basically feature complete, you could still use this.
However, the rx_webstreams library has even more awesome stream utilities, so check it out!

Useful Links:

• timerSource() Tests: https://github.com/codemonument/deno_rx_webstreams/blob/main/lib/sources/timerSource.test.ts

Note: The Explanation below does also work with timerSource() and is currently even better than in the rx_webstreams repository. So, feel free to use this right now.
I plan on releasing a full featured documentation site for rx_webstreams.
When that happens, I’ll update this readme with a link!

Original Readme

Description

A simple function which starts a timer with setInterval and returns a ReadableStream Instance (Web Streams).

Version 1.0.0 is considered feature complete right now. It will receive bugfixes, if I get notified of them or find the bugs myself. If someone has a nice feature which would greatly benefit this package, raise an issue or even better, submit a PR ! :)

Features

• Create a finite timerstream with 5 events, 1 per second per default
• Create a finite timerstream with x events, 1 per x ms (via options object)
• Create an infinite timerstream by passing an abortSignal into the options object

Simple Usage

Simply start a simpleTimerStream by calling its function: simpleTimerStream().
Per default, it will emit 5 events, 1 per second.

These Events can be read simply via a for await loop:

for await (const eventCount of simpleTimerStream()) {
    console.log(event);
}

Parametrized Usage

To change the maxEventsCount and intervalInMilliseconds values, simply pass an options object into simpleTimerStream():

const timer = simpleTimerStream({
    intervalInMilliseconds: 500,
    maxEventCount: 5,
});

for await (const event of timer) {
    console.log(event);
}

Usage with abort controller (infinite mode)

To use this simpleTimerStream() with an abort controller, simply pass an abortSignal into the options:

const abortController = new AbortController();

const timer = simpleTimerStream({
    intervalInMilliseconds: 1000,
    abortSignal: abortController.signal,
});

for await (const event of timer) {
    console.log(event);
}

This timer stream will go until you call abortController.abort(). Please note that you can’t call abortController.abort() in the same function below the for await statement, since this for await statement blocks execution of the function indefinitely.

One solution to this problem would be to define the condition, where the abort controller should abort, above the for await structure. I’m using a setTimeout in this examle:

const abortController = new AbortController();

const timeoutId = setTimeout(() => {
    abortController.abort();
}, 4500);

const timer = simpleTimerStream({
    intervalInMilliseconds: 1000,
    abortSignal: abortController.signal,
});

for await (const event of timer) {
    console.log(event);
}

// this is necessary to not have dangling async listeners in deno tests
clearTimeout(timeoutId);

Useful for

• Testing custom WriteableStream Instances!