ExponentialBackoff based on https://godoc.org/github.com/cenkalti/backoff#pkg-examples

ExponentialBackoff.js

// Reference: https://godoc.org/github.com/cenkalti/backoff#pkg-examples
// expect the following object to pass to constructor
// {
// 	retryInterval,
//	randomizationFactor,
//	multiplier,
//	maxInterval,
//	maxElapsedTime
// }
function ExponentialBackoff(data) {

	this.originalRetryInterval = data.retryInterval || 0.5;
	this.retryInterval = data.retryInterval || 500;	// default value is 500 milliseconds. In milliseconds
	this.randomizationFactor = data.randomizationFactor || 0.5;
	this.multiplier = data.multiplier || 1.5;
	if (this.multiplier <= 1) {
		throw new Error("multiplier must be greater than 1.");
	}
	this.maxInterval = data.maxInterval || 60 * 1000;	// 60 seconds /60000 milliseconds. In milliseconds
	this.maxElapsedTime = data.maxElapsedTime || 15 * 60 * 1000;	// 15 minutes/ 900000 milliseconds. In milliseconds
	this.startTime = new Date().getTime();
}

/*
Request #  RetryInterval (seconds)  Randomized Interval (seconds)

 1          0.5                     [0.25,   0.75]
 2          0.75                    [0.375,  1.125]
 3          1.125                   [0.562,  1.687]
 4          1.687                   [0.8435, 2.53]
 5          2.53                    [1.265,  3.795]
 6          3.795                   [1.897,  5.692]
 7          5.692                   [2.846,  8.538]
 8          8.538                   [4.269, 12.807]
 9         12.807                   [6.403, 19.210]
10         19.210                   backoff.Stop
*/

ExponentialBackoff.prototype.nextBackoff = function() {

	// If the time elapsed since an ExponentialBackOff instance is created goes past the MaxElapsedTime, then the method NextBackOff() starts returning backoff.Stop.
	if (this.getElapsedTime() > this.maxElapsedTime) {
		return this.STOP;
	}

	this.retryInterval = this.retryInterval * this.multiplier;
	if (this.retryInterval > this.maxInterval) {
		this.retryInterval = this.maxInterval;
	}

	// Randomized interval = RetryInterval +/- (RandomizationFactor * RetryInterval)
	var delta = this.randomizationFactor * this.retryInterval;
	var minInterval = this.retryInterval - delta;
	var maxInterval = this.retryInterval + delta;

	var randValue = Math.floor(Math.random() * (maxInterval - minInterval) + minInterval);
	console.log({backoffDelay: randValue});
	return randValue;
}

ExponentialBackoff.prototype.reset = function() {
	// Reset the interval back to the initial retry interval and restarts the timer.
	this.retryInterval = this.originalRetryInterval;
	this.startTime = new Date().getTime();
}

ExponentialBackoff.prototype.getElapsedTime = function() {
	var currentTime = new Date().getTime();
	var elapsedTime = currentTime - this.startTime;
	console.log( { elapsedTime: elapsedTime });
	return elapsedTime;
}

ExponentialBackoff.prototype.STOP = -1;