sequential-promise-map - npm Package Compare versions

Comparing version 1.1.0 to 1.2.0

package.json

 {
   "name": "sequential-promise-map",
-  "version": "1.1.0",
+  "version": "1.2.0",
   "description": "A simple sequential version of Promise.map",
@@ -5,0 +5,0 @@ "main": "src/sequential-promise-map.js",

README.md

@@ -16,8 +16,7 @@ # sequential-promise-map
 ```js
-sequentialPromiseMap(arrayOfValues, promiseGenerator).then(....) 
-
+sequentialPromiseMap(arrayOfValues, promiseGenerator, /*batchSize*/).then(....) 
 ```
 
-the `promiseGenerator` parameter should be a function:
-
+* `arrayOfValues` should be an `Array` of elements that will be asynchronously processed
+* `promiseGenerator` parameter should be a function to process each element of the array, receiving up to three arguments:
 ```js
@@ -28,4 +27,5 @@ promiseGenerator = function(currentElement, indexOfCurrent, originalArray) {
 ```
+* `batchSize` is an optional argument, a positive integer specifying the maximum batch size for parallel processing. If not set, the elements will be processed one by one. Set this to a value greater than 1 to allow for parallelisation. 
 
-The function will resolve will contain an array of Promise results, in the same order as the arguments, or reject with the first rejection.
+The function will resolve will contain an array of `Promise` results, in the same order as the arguments, or reject with the first rejection.
 
@@ -32,0 +32,0 @@

src/sequential-promise-map.js

@@ -1,2 +0,2 @@
-module.exports = function sequentialPromiseMap(array, generator) {
+module.exports = function sequentialPromiseMap(array, generator, batchArg) {
 	'use strict';
@@ -9,18 +9,22 @@ if (!Array.isArray(array)) {
 	}
-	let index = 0;
-	const results = [],
-		items = (array && array.slice()) || [],
-		sendSingle = function (item) {
-			return generator(item, index++, array)
-			.then(result => results.push(result));
+	if (batchArg && (!Number.isInteger(batchArg) || batchArg < 1)) {
+		throw new Error('the third argument must be undefined or a positive integer');
+	}
+	const batchSize = batchArg || 1,
+		results = [],
+		processBatch = function (batch, startIndex) {
+			const shiftIndexAndProcess = (element, index) => generator(element, index + startIndex, array);
+			return Promise.all(batch.map(shiftIndexAndProcess));
 		},
-		sendAll = function () {
-			if (!items.length) {
-				return Promise.resolve(results);
-			} else {
-				return sendSingle(items.shift())
-				.then(sendAll);
+		sendNextBatch = function (startIndex) {
+			if (startIndex >= array.length) {
+				return Promise.resolve();
 			}
+			const next = array.slice(startIndex, startIndex + batchSize);
+			return processBatch(next, startIndex)
+				.then(nextResults => results.push.apply(results, nextResults))
+				.then(() => sendNextBatch(startIndex + batchSize));
 		};
-	return sendAll();
+	return sendNextBatch(0)
+		.then(() => results);
 };

No alert changes

Improved metrics

Total package byte prevSize

4590

22.37%

Lines of code

29

16%

No dependency changes