Added Batch helper

lib/batch.js

@@ -0,0 +1,58 @@
+
+/**
+ * Expose `Batch`.
+ */
+
+module.exports = Batch;
+
+/**
+ * Create a new Batch.
+ */
+
+function Batch() {
+  this.fns = [];
+  for (var i = 0, len = arguments.length; i < len; ++i) {
+    this.push(arguments[i]);
+  }
+}
+
+/**
+ * Queue a function.
+ *
+ * @param {Function} fn
+ * @return {Batch}
+ * @api public
+ */
+
+Batch.prototype.push = function(fn){
+  this.fns.push(fn);
+  return this;
+};
+
+/**
+ * Execute all queued functions in parallel,
+ * executing `cb(err, results)`.
+ *
+ * @param {Function} cb
+ * @return {Batch}
+ * @api public
+ */
+
+Batch.prototype.end = function(cb){
+  var pending = this.fns.length
+    , results = []
+    , done;
+
+  if (!this.fns.length) return cb(null, results);
+
+  this.fns.forEach(function(fn){
+    fn(function(err, res){
+      if (done) return;
+      if (err) return done = true, cb(err);
+      results.push(res);
+      --pending || cb(null, results);
+    });
+  });
+
+  return this;
+};