added helper functions for enqueuing promises

lib/function.js

@@ -2,7 +2,12 @@
 
 const toArray = require('./array').toArray;
 
-const argsToArray = fn => () => fn(toArray(arguments));
+const argsToArray = fn => {
+    // must not be a fat arrow since it breaks the arguments
+    return function () {
+        return fn(toArray(arguments));
+    };
+};
 
 const curry = fn => {
     return function curried () {
@@ -19,8 +24,70 @@ const curry = fn => {
 
 const combine = argsToArray(fns => fns.reverse().reduce((fnc, fn) => val => fnc(fn(val))));
 
+const promisify = fn => () => {
+    // copy passed arguments to a new array
+    const args = toArray(arguments);
+
+    return new Promise((resolve, reject) => {
+        // add a callback to the arguments, which resolves the promise with the result
+        args.push((err, data) => {
+            if (err) {
+                reject(err);
+            } else {
+                resolve(data);
+            }
+        });
+
+        // call the original function with our callback flavoured arguments
+        fn.apply(null, args);
+    });
+};
+
+/**
+ returns a function which executes promises one after another
+ @param promiseGenerators an array of functions which return a promise
+ @return function which executes the promises
+ */
+const enqueue = (promiseGenerators) => {
+    return promiseGenerators.reduce((f, promiseGenerator) => {
+        return () => {
+            return f().then(promiseGenerator);
+        };
+    });
+};
+
+/**
+ Returns a function which executes promises one after another. The resulting function
+ returns a promise, which gets filled with an array of the results of the single promises.
+ @param promiseGenerators an array of functions which return a promise
+ @return function which executes the promises
+ */
+const enqueueWithResults = (function () {
+    const fnQueue = (results, promiseGenerators) => promiseGenerators.reduce((f, promiseGenerator) => {
+        return () => {
+            return f().then(result => {
+                results.push(result);
+                return promiseGenerator();
+            });
+        };
+    });
+
+    return function (promiseGenerators) {
+        return () => {
+            const results = [];
+            return fnQueue(results, promiseGenerators)().then(result => {
+                results.push(result);
+                return results;
+            });
+        };
+    };
+}());
+
 module.exports = {
     argsToArray,
     combine,
-    curry
+    curry,
+    promisify,
+    enqueue,
+    enqueueWithResults
 };