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@asanrom/async-tools

v2.0.0

Published

Collection of tools to work with async functions.

Downloads

241

Readme

Async tools

npm version

Collection of tools to work with async funcions in javascript.

Installation

If you are using a npm managed project use:

npm install @asanrom/async-tools

If you are using it in the browser, download the minified file from the Releases section and import it to your html:

<script type="text/javascript" src="/path/to/async-tools.js"></script>

The browser library exports all artifacts to the window global: AsyncTools

Async Interval

Interval that waits for the async function to end before runnng it again. Prevent multiple simultaneous executions.

Example use case: Async periodic task

Usage:

import { AsyncInterval } from "@asanrom/async-tools";

const interval = new AsyncInterval(async function () {
    await doSomethingAsync();
}, 1000 /* Milliseconds */);

interval.on("error", error => {
    // If the promise is rejected it will emit
    // and error event. If you want the interval to continue
    // when this happens, you have to assign an error handler
    console.error(error);
});

interval.start(); // Start the interval

interval.stop(); // Stops / Clears the interval

Async Queue

Queue with an async item handler.

  • Items are handled in order (FIFO)
  • If the handler is an async function, it waits for it to finish before dispatching the next item

Usage:

import { AsyncQueue } from "@asanrom/async-tools";

const queue = new AsyncQueue(
    MAX_SIZE, // Max size of the queue or 0 for unlimited size
    async function (item) { // Item handler
        await doSomethingAsync(item)
    }
);

queue.on("error", error => {
    // If the promise is rejected it will emit
    // and error event. If you want the queue to continue
    // when this happens, you have to assign an error handler
    console.error(error);
});

const items = [1, 2, 3, 4];
items.forEach(item => {
    // Use push(item) to push items to the queue
    // They will be dispatched automatically
    // Push will return false if the item was dropped
    queue.push(item);
});

// We can check the size of the queue (number of items in it)
queue.getCurrentSize();

// Also we can check if it's full
queue.isFull();

// If we want to release the resources of the queue
// we can call destroy()
// It returns a promise that waits if there is an item
// in the mid of being handled
await queue.destroy();

Async Semaphore

Semaphore to create critical sections on async functions.

Usage:

import { AsyncSemaphore } from "@asanrom/async-tools";


const sem = new AsyncSemaphore(); // Without params, initial instances is 1 (Mutex)
const sem3Instances = new AsyncSemaphore(3); // 3 initial instances

// Acquire instances, if it can't acquire
// the promise will resolve when the instances are available
// it will reject if the semaphore is destroyed
await sem.acquire();

// Release instances and resolve the promises
sem.release();

// Rejects all promises waiting to acquire the semaphore
// After destroyed, it cannot be used anymore
sem.destroy();

Async Provider

Provides values asynchronously, allowing a function to await the value while other function eventually provides the value.

It also provides a timeout option to set a max time to wait for the value.

Usage:

import { AsyncProvider } from "@asanrom/async-tools";

// Create a provider
const provider = new AsyncProvider(2000 /* Timeout in milliseconds as the constructor argument */);

server.on("message", msg => {
    // You can asynchronously provide a value.
    // For example, when an event is received
    provider.provideValue(msg);
});


server.on("error", err => {
    // You can also asynchronously provide an error
    provider.provideError(err);
});

try {
    // You can await for the value
    // The promise will be resolved if 'provideValue' is called on time
    // The promise will reject if the timeout is reached or 'provideError' is called
    const value = await provider.getValue();

    console.log("Value: " + value);
} catch (ex) {
    if (AsyncProvider.isTimeoutError(ex)) { // Check if the error is a timeout error
        // Timeout error
        console.error("The value was not provided in time!");
    } else {
        // Provided error
        console.error(ex);
    }
}

Documentation