optimize auto, parallel, and waterfall by not useing rest()

4 files changed, 28 insertions, 17 deletions

diff --git a/lib/auto.js b/lib/auto.js
index ba0fdc3..d712cc1 100644
--- a/lib/auto.js
+++ b/lib/auto.js
@@ -4,7 +4,7 @@ import indexOf from 'lodash/_baseIndexOf';
 import isArray from 'lodash/isArray';
 import okeys from 'lodash/keys';
 import noop from 'lodash/noop';
-import rest from './internal/rest';
+import slice from 'lodash/slice';
 
 import once from './internal/once';
 import onlyOnce from './internal/onlyOnce';
@@ -192,26 +192,26 @@ export default function (tasks, concurrency, callback) {
     function runTask(key, task) {
         if (hasError) return;
 
-        var taskCallback = onlyOnce(rest(function(err, args) {
+        var taskCallback = onlyOnce(function(err, result) {
             runningTasks--;
-            if (args.length <= 1) {
-                args = args[0];
+            if (arguments.length > 2) {
+                result = slice(arguments, 1);
             }
             if (err) {
                 var safeResults = {};
                 forOwn(results, function(val, rkey) {
                     safeResults[rkey] = val;
                 });
-                safeResults[key] = args;
+                safeResults[key] = result;
                 hasError = true;
                 listeners = Object.create(null);
 
                 callback(err, safeResults);
             } else {
-                results[key] = args;
+                results[key] = result;
                 taskComplete(key);
             }
-        }));
+        });
 
         runningTasks++;
         var taskFn = wrapAsync(task[task.length - 1]);
diff --git a/lib/internal/parallel.js b/lib/internal/parallel.js
index 70993d3..f4e9347 100644
--- a/lib/internal/parallel.js
+++ b/lib/internal/parallel.js
@@ -1,6 +1,6 @@
 import noop from 'lodash/noop';
 import isArrayLike from 'lodash/isArrayLike';
-import rest from './rest';
+import slice from './slice';
 import wrapAsync from './wrapAsync';
 
 export default function _parallel(eachfn, tasks, callback) {
@@ -8,13 +8,13 @@ export default function _parallel(eachfn, tasks, callback) {
     var results = isArrayLike(tasks) ? [] : {};
 
     eachfn(tasks, function (task, key, callback) {
-        wrapAsync(task)(rest(function (err, args) {
-            if (args.length <= 1) {
-                args = args[0];
+        wrapAsync(task)(function (err, result) {
+            if (arguments.length > 2) {
+                result = slice(arguments, 1);
             }
-            results[key] = args;
+            results[key] = result;
             callback(err);
-        }));
+        });
     }, function (err) {
         callback(err, results);
     });
diff --git a/lib/internal/slice.js b/lib/internal/slice.js
new file mode 100644
index 0000000..cd2e5b3
--- /dev/null
+++ b/lib/internal/slice.js
@@ -0,0 +1,9 @@
+export default function slice(arrayLike, start) {
+    start = start|0;
+    var newLen = Math.max(arrayLike.length - start, 0);
+    var newArr = Array(newLen);
+    for(var idx = 0; idx < newLen; idx++)  {
+        newArr[idx] = arrayLike[start + idx];
+    }
+    return newArr;
+}
diff --git a/lib/waterfall.js b/lib/waterfall.js
index 24befac..bfcf7a4 100644
--- a/lib/waterfall.js
+++ b/lib/waterfall.js
@@ -2,6 +2,7 @@ import isArray from 'lodash/isArray';
 import noop from 'lodash/noop';
 import once from './internal/once';
 import rest from './internal/rest';
+import slice from './internal/slice';
 
 import onlyOnce from './internal/onlyOnce';
 import wrapAsync from './internal/wrapAsync';
@@ -74,12 +75,13 @@ export default  function(tasks, callback) {
             return callback.apply(null, [null].concat(args));
         }
 
-        var taskCallback = onlyOnce(rest(function(err, args) {
+        var taskCallback = onlyOnce(function(err/*, cbArgs...*/) {
+            var cbArgs = slice(arguments, 1);
             if (err) {
-                return callback.apply(null, [err].concat(args));
+                return callback.apply(null, [err].concat(cbArgs));
             }
-            nextTask(args);
-        }));
+            nextTask(cbArgs);
+        });
 
         args.push(taskCallback);