asyncbox

A collection of ES7 async/await utilities. Install via NPM:

npm install asyncbox

Then, behold!

Sleep

An async/await version of setTimeout

import { sleep } from 'asyncbox';

async function myFn () {
    // do some stuff
    await sleep(1000); // wait one second
    // do some other stuff
};

Retry

An async/await way of running a method until it doesn't throw an error

import { sleep, retry } from 'asyncbox';

async function flakeyFunction (val1, val2) {
    if (val1 < 10) {
        throw new Error("this is a flakey value");
    }
    await sleep(1000);
    return val1 + val2;
}

async function myFn () {
    let randVals = [Math.random() * 100, Math.random() * 100];

    // run flakeyFunction up to 3 times until it succeeds.
    // if it doesn't, we'll get the error thrown in this context
    let randSum = await retry(3, flakeyFunction, ...randVals);
}

You can also use retryInterval to add a sleep in between retries. This can be useful if you want to throttle how fast we retry:

await retryInterval(3, 1500, expensiveFunction, ...args);

Filter/Map

Filter and map are pretty handy concepts, and now you can write filter and map functions that execute asynchronously!

import { asyncmap, asyncfilter } from 'asyncbox';

Then in your async functions, you can do:

const items = [1, 2, 3, 4];
const slowSquare = async (n) => { await sleep(5); return n * 2; };
let newItems = await asyncmap(items, async (i) => { return await slowSquare(i); });
console.log(newItems);  // [1, 4, 9, 16];

const slowEven = async (n) => { await sleep(5); return n % 2 === 0; };
newItems = await asyncfilter(items, async (i) => { return await slowEven(i); });
console.log(newItems); // [2, 4];

By default, asyncmap and asyncfilter run their operations in parallel; you can pass false as a third argument to make sure it happens serially.

Nodeify

Export async functions (Promises) and import this with your ES5 code to use it with Node.

var asyncbox = require('asyncbox')
  , sleep = asyncbox.sleep
  , nodeify = asyncbox.nodeify;

nodeify(sleep(1000), function (err, timer) {
  console.log(err); // null
  console.log(timer); // timer obj
});

nodeifyAll

If you have a whole library you want to export nodeified versions of, it's pretty easy:

import { nodeifyAll } from 'asyncbox';

async function foo () { ... }
async function bar () { ... }
let cb = nodeifyAll({foo, bar});
export { foo, bar, cb };

Then in my ES5 script I can do:

var myLib = require('mylib').cb;

myLib.foo(function (err) { ... });
myLib.bar(function (err) { ... });

waitForCondition

Takes a condition (a function returning a boolean or boolean promise), and waits until the condition is true.

Throws a /Condition unmet/ error if the condition has not been satisfied within the allocated time.

The default options are: { waitMs: 5000, intervalMs: 500 }

// define your own condition
function condFn () { return Math.random()*1000 > 995; }

// with default params
await waitForCondition(condFn);

// with options
await waitForCondition(condFn, {
  waitMs: 300000,
  intervalMs: 10000
});

// pass a logger to get extra debug info
await waitForCondition(condFn, {
  waitMs: 300000,
  intervalMs: 10000
  logger: myLogger // expects a debug method
});

Run the tests

npm test

deep9/asyncbox