Example 3-13. Build sequential chain using recursion

// Replaces sequence in previous example with a recursive implementation
function sequence(array, callback) {
	function chain(array, index) {
		if (index == array.length) return Promise.resolve();
		return Promise.resolve(callback(array[index])).then(function () {
			return chain(array, index + 1);
		});
	}
	return chain(array, 0);
}

// Console output is identical to Example 3-12
// Requested info for sku-1
// Info for sku-1
// Requested info for sku-2
// Info for sku-2
// Requested info for sku-3
// Info for sku-3