Simple Async busy wait module for Node.JS

This module is installed via npm:

npm install --save busywait

Running:

const busywait = require('../lib/index').sync;

const waitUntil = Date.now() + 2500;

function syncCheck(iteration) {
    console.log('running iteration', iteration);
    return Date.now() > waitUntil;
}

busywait(syncCheck, {
    sleepTime: 500,
    maxChecks: 20
})
    .then(function (result) {
        console.log('finished after', result.iterations, 'iterations', 'with' +
            ' result', result.result);
    });

or:

const busywait = require('../lib/index').async;

const waitUntil = Date.now() + 2500;

function asyncCheck(iteration) {
    return new Promise(function (resolve, reject) {
        console.log('running iteration', iteration);
        if (Date.now() > waitUntil) {
            return resolve(true);
        } else {
            return reject();
        }
    });
}

busywait(asyncCheck, {
    sleepTime: 500,
    maxChecks: 20
})
    .then(function (result) {
        console.log('finished after', result.iterations, 'iterations', 'with' +
            ' result', result.result);
    });

Will result in:

running iteration 1
running iteration 2
running iteration 3
running iteration 4
running iteration 5
running iteration 6
finished after 6 iterations with result true

The syncCheckFn first argument is the function to run on each iteration. syncCheckFn must be a function with a boolean return value. The current iteration number will be passed as first argument to every call of syncCheckFn.

• sleepTime - Time in ms to wait between checks
• maxChecks - The max number of checks to perform before failing

• waitFirst - Should we wait the sleepTime before performing the first check (default: false)
• failMsg - Custom error message to reject the promise with

Return value is a promise.

• The promise will be resolved if the syncCheckFn returned true within a legal number of checks.
• The promise will be rejected if the syncCheckFn rejected maxChecks times.

Promise resolved value:

• iterations - The number of iterations it took to finish
• result - Constant true

The asyncCheckFn first argument is the function to run on each iteration. syncCheckFn must be a function with a promise return value. The current iteration number will be passed as first argument to every call of asyncCheckFn.

• sleepTime - Time in ms to wait between checks
• maxChecks - The max number of checks to perform before failing

• waitFirst - Should we wait the sleepTime before performing the first check (default: false)
• failMsg - Custom error message to reject the promise with

Return value is a promise.

• The promise will be resolved if the asyncCheckFn was resolved within a legal number of checks.
• The promise will be rejected if the asyncCheckFn rejected maxChecks times.

Promise resolved value:

• iterations - The number of iterations it took to finish
• result - The resolved value of asyncCheckFn

Please make all pull requests to the master branch and ensure tests pass locally.