Optimized waterfall, parallel, et al.

lib/apply.js

@@ -1,4 +1,4 @@
-import rest from './internal/rest';
+import slice from './internal/slice';
 
 /**
  * Creates a continuation function with some arguments already applied.
@@ -12,10 +12,11 @@ import rest from './internal/rest';
  * @memberOf module:Utils
  * @method
  * @category Util
- * @param {Function} function - The function you want to eventually apply all
+ * @param {Function} fn - The function you want to eventually apply all
  * arguments to. Invokes with (arguments...).
  * @param {...*} arguments... - Any number of arguments to automatically apply
  * when the continuation is called.
+ * @returns {Function} the partially-applied function
  * @example
  *
  * // using apply
@@ -44,8 +45,10 @@ import rest from './internal/rest';
  * two
  * three
  */
-export default rest(function(fn, args) {
-    return rest(function(callArgs) {
+export default function(fn/*, args*/) {
+    var args = slice(arguments, 1);
+    return function(/*callArgs*/) {
+        var callArgs = slice(arguments);
         return fn.apply(null, args.concat(callArgs));
-    });
-});
+    };
+};

lib/auto.js

@@ -4,8 +4,8 @@ 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 './internal/slice';
 import once from './internal/once';
 import onlyOnce from './internal/onlyOnce';
 import wrapAsync from './internal/wrapAsync';
@@ -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]);

lib/compose.js

@@ -1,5 +1,5 @@
 import seq from './seq';
-import rest from './internal/rest';
+import slice from './internal/slice';
 
 /**
  * Creates a function which is a composition of the passed asynchronous
@@ -36,6 +36,6 @@ import rest from './internal/rest';
  *     // result now equals 15
  * });
  */
-export default rest(function(args) {
-    return seq.apply(null, args.reverse());
-});
+export default function(/*...args*/) {
+    return seq.apply(null, slice(arguments).reverse());
+};

lib/constant.js

@@ -1,5 +1,4 @@
-import rest from './internal/rest';
-import initialParams from './internal/initialParams';
+import slice from './internal/slice';
 
 /**
  * Returns a function that when called, calls-back with the values provided.
@@ -43,9 +42,11 @@ import initialParams from './internal/initialParams';
  *     //...
  * }, callback);
  */
-export default rest(function(values) {
+export default function(/*...values*/) {
+    var values = slice(arguments);
     var args = [null].concat(values);
-    return initialParams(function (ignoredArgs, callback) {
+    return function (/*...ignoredArgs, callback*/) {
+        var callback = arguments[arguments.length - 1];
         return callback.apply(this, args);
-    });
-});
+    };
+};

lib/doDuring.js

@@ -1,5 +1,5 @@
 import noop from 'lodash/noop';
-import rest from './internal/rest';
+import slice from './internal/slice';
 import onlyOnce from './internal/onlyOnce';
 import wrapAsync from './internal/wrapAsync';
 
@@ -28,11 +28,12 @@ export default function doDuring(fn, test, callback) {
     var _fn = wrapAsync(fn);
     var _test = wrapAsync(test);
 
-    var next = rest(function(err, args) {
-        if (err)  return callback(err);
+    function next(err/*, ...args*/) {
+        if (err) return callback(err);
+        var args = slice(arguments, 1);
         args.push(check);
         _test.apply(this, args);
-    });
+    };
 
     function check(err, truth) {
         if (err) return callback(err);

lib/doWhilst.js

@@ -1,5 +1,5 @@
 import noop from 'lodash/noop';
-import rest from './internal/rest';
+import slice from './internal/slice';
 
 import onlyOnce from './internal/onlyOnce';
 import wrapAsync from './internal/wrapAsync';
@@ -29,10 +29,11 @@ import wrapAsync from './internal/wrapAsync';
 export default function doWhilst(iteratee, test, callback) {
     callback = onlyOnce(callback || noop);
     var _iteratee = wrapAsync(iteratee);
-    var next = rest(function(err, args) {
+    var next = function(err/*, ...args*/) {
         if (err) return callback(err);
+        var args = slice(arguments, 1);
         if (test.apply(this, args)) return _iteratee(next);
         callback.apply(null, [null].concat(args));
-    });
+    };
     _iteratee(next);
 }

lib/internal/applyEach.js

@@ -1,9 +1,10 @@
-import rest from './rest';
+import slice from './slice';
 import initialParams from './initialParams';
 import wrapAsync from './wrapAsync';
 
 export default function applyEach(eachfn) {
-    return rest(function(fns, args) {
+    return function(fns/*, ...args*/) {
+        var args = slice(arguments, 1);
         var go = initialParams(function(args, callback) {
             var that = this;
             return eachfn(fns, function (fn, cb) {
@@ -16,5 +17,5 @@ export default function applyEach(eachfn) {
         else {
             return go;
         }
-    });
+    };
 }

lib/internal/consoleFunc.js

@@ -1,10 +1,12 @@
 import arrayEach from 'lodash/_arrayEach';
-import rest from './rest';
+import slice from './slice';
 import wrapAsync from './wrapAsync';
 
 export default function consoleFunc(name) {
-    return rest(function (fn, args) {
-        wrapAsync(fn).apply(null, args.concat(rest(function (err, args) {
+    return function (fn/*, ...args*/) {
+        var args = slice(arguments, 1);
+        wrapAsync(fn).apply(null, args.concat(function (err/*, ...args*/) {
+            var args = slice(arguments, 1);
             if (typeof console === 'object') {
                 if (err) {
                     if (console.error) {
@@ -17,6 +19,6 @@ export default function consoleFunc(name) {
                     });
                 }
             }
-        })));
-    });
+        }));
+    };
 }

lib/internal/initialParams.js

@@ -1,8 +1,9 @@
-import rest from './rest';
+import slice from './slice';
 
 export default function (fn) {
-    return rest(function (args/*..., callback*/) {
+    return function (/*...args, callback*/) {
+        var args = slice(arguments);
         var callback = args.pop();
         fn.call(this, args, callback);
-    });
+    };
 }

lib/internal/parallel.js

@@ -1,20 +1,20 @@
 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) {
     callback = callback || noop;
     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);
     });

lib/internal/queue.js

@@ -1,7 +1,6 @@
 import indexOf from 'lodash/_baseIndexOf';
 import isArray from 'lodash/isArray';
 import noop from 'lodash/noop';
-import rest from './rest';
 
 import onlyOnce from './onlyOnce';
 import setImmediate from './setImmediate';
@@ -51,7 +50,7 @@ export default function queue(worker, concurrency, payload) {
     }
 
     function _next(tasks) {
-        return rest(function(args){
+        return function(err){
             numRunning -= 1;
 
             for (var i = 0, l = tasks.length; i < l; i++) {
@@ -61,10 +60,10 @@ export default function queue(worker, concurrency, payload) {
                     workersList.splice(index)
                 }
 
-                task.callback.apply(task, args);
+                task.callback.apply(task, arguments);
 
-                if (args[0] != null) {
-                    q.error(args[0], task.data);
+                if (err != null) {
+                    q.error(err, task.data);
                 }
             }
 
@@ -76,7 +75,7 @@ export default function queue(worker, concurrency, payload) {
                 q.drain();
             }
             q.process();
-        });
+        };
     }
 
     var isProcessing = false;

lib/internal/setImmediate.js

@@ -1,6 +1,6 @@
 'use strict';
 
-import rest from './rest';
+import slice from './slice';
 
 export var hasSetImmediate = typeof setImmediate === 'function' && setImmediate;
 export var hasNextTick = typeof process === 'object' && typeof process.nextTick === 'function';
@@ -10,11 +10,12 @@ export function fallback(fn) {
 }
 
 export function wrap(defer) {
-    return rest(function (fn, args) {
+    return function (fn/*, ...args*/) {
+        var args = slice(arguments, 1);
         defer(function () {
             fn.apply(null, args);
         });
-    });
+    };
 }
 
 var _defer;

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;
+}

lib/memoize.js

@@ -1,5 +1,5 @@
 import identity from 'lodash/identity';
-import rest from './internal/rest';
+import slice from './internal/slice';
 
 import setImmediate from './internal/setImmediate';
 import initialParams from './internal/initialParams';
@@ -61,14 +61,15 @@ export default function memoize(fn, hasher) {
             queues[key].push(callback);
         } else {
             queues[key] = [callback];
-            _fn.apply(null, args.concat(rest(function(args) {
+            _fn.apply(null, args.concat(function(/*args*/) {
+                var args = slice(arguments);
                 memo[key] = args;
                 var q = queues[key];
                 delete queues[key];
                 for (var i = 0, l = q.length; i < l; i++) {
                     q[i].apply(null, args);
                 }
-            })));
+            }));
         }
     });
     memoized.memo = memo;

lib/reduceRight.js

@@ -1,6 +1,5 @@
 import reduce from './reduce';
-
-var slice = Array.prototype.slice;
+import slice from './internal/slice';
 
 /**
  * Same as [`reduce`]{@link module:Collections.reduce}, only operates on `array` in reverse order.
@@ -25,6 +24,6 @@ var slice = Array.prototype.slice;
  * (err, result).
  */
 export default function reduceRight (array, memo, iteratee, callback) {
-    var reversed = slice.call(array).reverse();
+    var reversed = slice(array).reverse();
     reduce(reversed, memo, iteratee, callback);
 }