added unit testing, and started implementing unit tests...phew

node_modules/async/waterfall.js

@@ -0,0 +1,113 @@
+'use strict';
+
+Object.defineProperty(exports, "__esModule", {
+    value: true
+});
+
+exports.default = function (tasks, callback) {
+    callback = (0, _once2.default)(callback || _noop2.default);
+    if (!(0, _isArray2.default)(tasks)) return callback(new Error('First argument to waterfall must be an array of functions'));
+    if (!tasks.length) return callback();
+    var taskIndex = 0;
+
+    function nextTask(args) {
+        var task = (0, _wrapAsync2.default)(tasks[taskIndex++]);
+        args.push((0, _onlyOnce2.default)(next));
+        task.apply(null, args);
+    }
+
+    function next(err /*, ...args*/) {
+        if (err || taskIndex === tasks.length) {
+            return callback.apply(null, arguments);
+        }
+        nextTask((0, _slice2.default)(arguments, 1));
+    }
+
+    nextTask([]);
+};
+
+var _isArray = require('lodash/isArray');
+
+var _isArray2 = _interopRequireDefault(_isArray);
+
+var _noop = require('lodash/noop');
+
+var _noop2 = _interopRequireDefault(_noop);
+
+var _once = require('./internal/once');
+
+var _once2 = _interopRequireDefault(_once);
+
+var _slice = require('./internal/slice');
+
+var _slice2 = _interopRequireDefault(_slice);
+
+var _onlyOnce = require('./internal/onlyOnce');
+
+var _onlyOnce2 = _interopRequireDefault(_onlyOnce);
+
+var _wrapAsync = require('./internal/wrapAsync');
+
+var _wrapAsync2 = _interopRequireDefault(_wrapAsync);
+
+function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
+
+module.exports = exports['default'];
+
+/**
+ * Runs the `tasks` array of functions in series, each passing their results to
+ * the next in the array. However, if any of the `tasks` pass an error to their
+ * own callback, the next function is not executed, and the main `callback` is
+ * immediately called with the error.
+ *
+ * @name waterfall
+ * @static
+ * @memberOf module:ControlFlow
+ * @method
+ * @category Control Flow
+ * @param {Array} tasks - An array of [async functions]{@link AsyncFunction}
+ * to run.
+ * Each function should complete with any number of `result` values.
+ * The `result` values will be passed as arguments, in order, to the next task.
+ * @param {Function} [callback] - An optional callback to run once all the
+ * functions have completed. This will be passed the results of the last task's
+ * callback. Invoked with (err, [results]).
+ * @returns undefined
+ * @example
+ *
+ * async.waterfall([
+ *     function(callback) {
+ *         callback(null, 'one', 'two');
+ *     },
+ *     function(arg1, arg2, callback) {
+ *         // arg1 now equals 'one' and arg2 now equals 'two'
+ *         callback(null, 'three');
+ *     },
+ *     function(arg1, callback) {
+ *         // arg1 now equals 'three'
+ *         callback(null, 'done');
+ *     }
+ * ], function (err, result) {
+ *     // result now equals 'done'
+ * });
+ *
+ * // Or, with named functions:
+ * async.waterfall([
+ *     myFirstFunction,
+ *     mySecondFunction,
+ *     myLastFunction,
+ * ], function (err, result) {
+ *     // result now equals 'done'
+ * });
+ * function myFirstFunction(callback) {
+ *     callback(null, 'one', 'two');
+ * }
+ * function mySecondFunction(arg1, arg2, callback) {
+ *     // arg1 now equals 'one' and arg2 now equals 'two'
+ *     callback(null, 'three');
+ * }
+ * function myLastFunction(arg1, callback) {
+ *     // arg1 now equals 'three'
+ *     callback(null, 'done');
+ * }
+ */