Execute promises sequentially in batches

batch-promise.js

var Q = require('q');

function batchPromises(items, fn, options) {
	var results = [];
	var index = (options.batchSize - 1);

	function getNextItem() {
		index++;
		if (items.length > index) {                
			var nextItem = items[index];
			return getCurrentItem(nextItem);
		} 
	}

	function getCurrentItem(item) {
		console.log(item, 'Starting');
		return fn(item)
			.then(function(result) {
				console.log(item, 'Success');
				results.push(result);
				return getNextItem();
			})
			.catch(function() {
				console.log(item, 'Error');
				return options.retry ? getCurrentItem(item) : getNextItem();
			});
	};
  

	var promises = items.slice(0, options.batchSize).map(function(item) {		
		return getCurrentItem(item);
	});
	return Q.all(promises).then(function() {
		return results;
	});
} 

function handler(item) {
	return Q.delay(400).then(function() {
		if (Math.random() > 0.5) {
			throw new Error('A random error occured');
		}
		return item;
	});
}
var options = {
	batchSize: 3,
	retry: true
}
batchPromises(['a', 'b', 'c', 'd', 'e', 'f'], handler, options).then(function(items) {
	console.log('Succeeded', items);
})