Added async.someLimit

When checking if a folder contains subfolders or not (fs.readdir -> fs.stat -> some(is_a_Folder)), getting crashes when listing Windows shares from Ubuntu VM. someLimit avoids the problem.

Test for someLimit

added anyLimit alias and updated doc.

removed anyLimit alias

README.md

@@ -172,8 +172,11 @@ Some functions are also available in the following forms:
 * [`reduce`](#reduce), [`reduceRight`](#reduceRight)
 * [`detect`](#detect), `detectSeries`
 * [`sortBy`](#sortBy)
-* [`some`](#some), [`every`](#every)
-* [`concat`](#concat), `concatSeries`
+* [`some`](#some)
+* [`someLimit`](#someLimit)
+* [`every`](#every)
+* [`concat`](#concat)
+* [`concatSeries`](#concatSeries)
 
 ### Control Flow
 
@@ -581,6 +584,27 @@ async.some(['file1','file2','file3'], fs.exists, function(result){
 
 ---------------------------------------
 
+<a name="someLimit" />
+### someLimit(arr, limit iterator, callback)
+
+__Alias:__ `anyLimit`
+
+The same as [`some`](#some), only no more than `limit` `iterator`s will be simultaneously 
+running at any time.
+
+__Arguments__
+
+* `arr` - An array to iterate over.
+* `limit` - The maximum number of `iterator`s to run at any time.
+* `iterator(item, callback)` - A truth test to apply to each item in the array
+  in parallel. The iterator is passed a callback(truthValue) which must be 
+  called with a boolean argument once it has completed.
+* `callback(result)` - A callback which is called as soon as any iterator returns
+  `true`, or after all the iterator functions have finished. Result will be
+  either `true` or `false` depending on the values of the async tests.
+
+---------------------------------------
+
 <a name="every" />
 ### every(arr, iterator, [callback])
 

lib/async.js

@@ -456,24 +456,34 @@
     async.detectSeries = doSeries(_detect);
 
     function _createTester(eachfn, check, defaultValue) {
-        return function(arr, iterator, main_callback) {
-            eachfn(arr, function (x, _, callback) {
+        return function(arr, limit, iterator, main_callback) {
+            function done() {
+                main_callback(defaultValue);
+            }
+            function iteratee(x, _, callback) {
                 iterator(x, function (v) {
                     if (check(v)) {
                         main_callback(!defaultValue);
                         main_callback = noop;
                     }
                     callback();
                 });
-            }, function () {
-                main_callback(defaultValue);
-            });
+            }
+            if (arguments.length > 3) {
+                eachfn(arr, limit, iteratee, done);
+            } else {
+                main_callback = iterator;
+                iterator = limit;
+                eachfn(arr, iteratee, done);
+            }
         };
     }
 
     async.any =
     async.some = _createTester(async.eachOf, identity, false);
 
+    async.someLimit = _createTester(async.eachOfLimit, identity, false);
+
     async.all =
     async.every = _createTester(async.eachOf, notId, true);
 

test/test-async.js

@@ -2236,6 +2236,24 @@ exports['some early return'] = function(test){
     }, 100);
 };
 
+exports['someLimit true'] = function(test){
+    async.someLimit([3,1,2], 2, function(x, callback){
+        setTimeout(function(){callback(x === 2);}, 0);
+    }, function(result){
+        test.equals(result, true);
+        test.done();
+    });
+};
+
+exports['someLimit false'] = function(test){
+    async.someLimit([3,1,2], 2, function(x, callback){
+        setTimeout(function(){callback(x === 10);}, 0);
+    }, function(result){
+        test.equals(result, false);
+        test.done();
+    });
+};
+
 exports['any alias'] = function(test){
     test.equals(async.any, async.some);
     test.done();