v1.0.3: use index as well

README.md

@@ -3,13 +3,17 @@
 Like calling `map()` and resolving with `Promise.all()`,
 but handling a bounded number of items at any given time.
 
-## Install
+Want to read about it?
+
+- [Batching async requests in < 50 lines of VanillaJS](https://coolaj86.com/articles/batching-async-requests-50-lines-of-vanilla-js/)
+
+# Install
 
 ```bash
 npm install --save batchasync
 ```
 
-## Usage
+# Usage
 
 ```js
 // Browsers
@@ -35,10 +39,14 @@ batchAsync(batchSize, things, doStuff).then(function(results) {
 });
 ```
 
-### Returning 'undefined'
+## A note on `undefined`
 
-Returning `undefined` will cause an exception to be thrown
+Returning `undefined` will cause an exception to be thrown,
-(because it looks like a skipped promise). Return `null` instead.
+and the Promise to be rejected.
+
+This is on purpose - because `undefined` is indistinguishable from a skipped Promise.
+
+Return `null` instead.
 
 **Example (bad)**:
 

batchasync.js

@@ -1,5 +1,5 @@
 (function(exports) {
-'use strict';
+    "use strict";
 
     exports.batchAsync = function(limit, arr, doStuff) {
         arr = arr.slice(0);
@@ -37,7 +37,7 @@ exports.batchAsync = function (limit, arr, doStuff) {
 
                 var p;
                 try {
-				p = doStuff(task);
+                    p = doStuff(task, index, arr);
                 } catch (e) {
                     // we need to handle, and bubble, synchronous errors
                     error = e;
@@ -48,7 +48,7 @@ exports.batchAsync = function (limit, arr, doStuff) {
                 // add support for sync by rapping in a promise
                 Promise.resolve(p)
                     .then(function(result) {
-					if ('undefined' === typeof result) {
+                        if ("undefined" === typeof result) {
                             throw new Error(
                                 "result was 'undefined'. Please return 'null' to signal that you didn't just forget to return another promise."
                             );
@@ -67,5 +67,4 @@ exports.batchAsync = function (limit, arr, doStuff) {
             doMoreStuff();
         });
     };
-
+})("undefined" !== typeof window ? window : module.exports);
-}('undefined' !== typeof window ? window : module.exports));

package-lock.json

@@ -0,0 +1,5 @@
+{
+  "name": "batchasync",
+  "version": "1.0.3",
+  "lockfileVersion": 1
+}

package.json

@@ -1,6 +1,6 @@
 {
   "name": "batchasync",
-  "version": "1.0.1",
+  "version": "1.0.3",
   "description": "Like forEachAsync, or Promise.all(), but handling a bounded number of items at any given time.",
   "main": "batchasync.js",
   "scripts": {

test.js

@@ -1,15 +1,17 @@
 (function(exports) {
-'use strict';
+    "use strict";
 
-var batchAsync = exports.batchAsync || require('./batchasync.js').batchAsync;
+    var batchAsync =
+        exports.batchAsync || require("./batchasync.js").batchAsync;
 
     function testBatch() {
         var timeouts = [100, 80, 20, 500, 50, 30, 200, 300];
+        console.info(timeouts);
         var tasks = timeouts.map(function(timeout, i) {
             return function() {
                 return promiseTimeout(timeout).then(function() {
-				console.log('task:', i, timeouts[i]);
+                    //console.log("task:", i, timeouts[i]);
-				return i;
+                    return i + ":" + timeouts[i];
                 });
             };
         });
@@ -19,40 +21,40 @@ function testBatch() {
             return task();
         })
             .then(function(results) {
-			console.info('results:', results);
+                console.info("results:", results);
                 if (len !== results.length) {
-				throw new Error('result set too small');
+                    throw new Error("result set too small");
                 }
-			if (results.join(' ') !== results.sort().join(' ')) {
+                if (results.join(" ") !== results.sort().join(" ")) {
-				throw new Error('result set out-of-order');
+                    throw new Error("result set out-of-order");
                 }
             })
             .then(function() {
-			return batchAsync(4, [], 'not a function').then(function() {
+                return batchAsync(4, [], "not a function").then(function() {
-				console.info('Handled ZERO tasks correctly.');
+                    console.info("Handled ZERO tasks correctly.");
                 });
             })
             .then(function() {
                 return batchAsync(4, timeouts, function(x) {
                     return x;
                 }).then(function(results) {
-				if (results.join(' ') !== timeouts.join(' ')) {
+                    if (results.join(" ") !== timeouts.join(" ")) {
                         console.error(results);
-					throw new Error('sync result set out-of-order');
+                        throw new Error("sync result set out-of-order");
                     }
-				console.info('Handled sync tasks correctly.');
+                    console.info("Handled sync tasks correctly.");
                 });
             })
             .then(function() {
                 return batchAsync(4, tasks, function(task) {
                     if (0 === Math.floor(Math.random() * 2) % 2) {
-					throw new Error('any async error will do');
+                        throw new Error("any async error will do");
                     }
                     return task();
                 })
                     .then(function(results) {
                         console.log(results);
-					var e = new Error('async rejection should not pass!');
+                        var e = new Error("async rejection should not pass!");
                         e.FAIL = true;
                         throw e;
                     })
@@ -60,18 +62,18 @@ function testBatch() {
                         if (e.FAIL) {
                             throw e;
                         }
-					console.info('Pass: Exception thrown when expected');
+                        console.info("Pass: Exception thrown when expected");
                     });
             })
             .then(function() {
                 return batchAsync(4, timeouts, function() {
                     if (0 === Math.floor(Math.random() * 2) % 2) {
-					throw new Error('any sync error will do');
+                        throw new Error("any sync error will do");
                     }
                     return null;
                 })
-				.then(function(results) {
+                    .then(function(/*results*/) {
-					var e = new Error('should not pass sync exception!');
+                        var e = new Error("should not pass sync exception!");
                         e.FAIL = true;
                         throw e;
                     })
@@ -82,29 +84,28 @@ function testBatch() {
                     })
                     .then(function() {
                         // wait for the tasks the error left dangling to print their message
-					console.info('Pass: Promise rejected when expected');
+                        console.info("Pass: Promise rejected when expected");
                         return promiseTimeout(1000);
                     });
             });
     }
 
     function promiseTimeout(timeout) {
-	return new Promise(function(resolve, reject) {
+        return new Promise(function(resolve) {
             setTimeout(resolve, timeout);
         });
     }
 
     testBatch()
         .then(function() {
-		console.info('PROBABLY PASSED');
+            console.info("PROBABLY PASSED");
             console.info(
-			'We tested what could be tested without knowing Passed what could be tested Do the results make sense?'
+                "We tested what could be tested. Do the results make sense?"
             );
         })
         .catch(function(e) {
-		console.error('FAIL!');
+            console.error("FAIL!");
             console.error(e);
             process.exit(500);
         });
-
+})("undefined" !== typeof window ? window : module.exports);
-}('undefined' !== typeof window ? window : module.exports));