Add Q.call, like nfcall but accepts a thisArg

Author: kylehg

README.md

@@ -254,7 +254,7 @@ Q.fcall(someFn, arg1, arg2)
 
 You can also use ``Q.fcall()`` with functions that return promises.
 
-### `.nfcall()` for Node.js callbacks
+### `.ncall()` and `.nfcall()` for Node.js callbacks
 
 ``Q.nfcall()`` can be used to convert node-style callbacks into promises:
 
@@ -268,6 +268,15 @@ Q.nfcall(fs.writeFile, '/tmp/myFile', 'content')
   })
 ```
 
+If your Node-style callback needs a `this` context, you can use `Q.ncall`:
+
+```js
+Q.ncall(redis.del, redis, 'my-key')
+  .then(function () { return true })
+  .fail(function () { return false })
+```
+
+
 ### `.spread()` for arrays of promises
 
 ``()`` can be used to convert node-style callbacks into promises:

kew.js

@@ -800,7 +800,20 @@ function nfcall(fn, var_args) {
   // Insert an undefined argument for scope and let bindPromise() do the work.
   var args = Array.prototype.slice.call(arguments, 0)
   args.splice(1, 0, undefined)
-  return bindPromise.apply(undefined, args)()
+  return ncall.apply(undefined, args)
+}
+
+
+/**
+ * Like `nfcall`, but permits passing a `this` context for the call.
+ *
+ * @param {function(...)} fn
+ * @param {Object} scope
+ * @param {...*} var_args
+ * @return {!Promise}
+ */
+function ncall(fn, scope, var_args) {
+  return bindPromise.apply(null, arguments)()
 }
 
 
@@ -827,20 +840,21 @@ function bindPromise(fn, scope, var_args) {
 }
 
 module.exports = {
-    all: all
-  , bindPromise: bindPromise
-  , defer: defer
-  , delay: delay
-  , fcall: fcall
-  , isPromise: isPromise
-  , isPromiseLike: isPromiseLike
-  , nfcall: nfcall
-  , resolve: resolve
-  , reject: reject
-  , spread: spread
-  , stats: stats
-  , allSettled: allSettled
-  , Promise: Promise
-  , getNextTickFunction: getNextTickFunction
-  , setNextTickFunction: setNextTickFunction
+  all: all,
+  bindPromise: bindPromise,
+  defer: defer,
+  delay: delay,
+  fcall: fcall,
+  isPromise: isPromise,
+  isPromiseLike: isPromiseLike,
+  ncall: ncall,
+  nfcall: nfcall,
+  resolve: resolve,
+  reject: reject,
+  spread: spread,
+  stats: stats,
+  allSettled: allSettled,
+  Promise: Promise,
+  getNextTickFunction: getNextTickFunction,
+  setNextTickFunction: setNextTickFunction,
 }

package.json

@@ -1,7 +1,7 @@
 {
   "name": "kew",
   "description": "a lightweight promise library for node",
-  "version": "0.6.0",
+  "version": "0.7.0",
   "homepage": "https://github.com/Medium/kew",
   "authors": [
     "Jeremy Stanley <[email protected]> (https://github.com/azulus)",

test/static.js

@@ -319,6 +319,23 @@ exports.testNFcallErrorSync = function (test) {
     })
 }
 
+exports.testNcall = function (test) {
+  function TwoAdder() {
+    this.a = 2
+  }
+  TwoAdder.prototype.add = function (num, callback) {
+    setTimeout(function () {
+      callback(null, this.a + num)
+    }.bind(this), 10)
+  }
+  var adder = new TwoAdder()
+  Q.ncall(adder.add, adder, 3)
+    .then(function (val) {
+      test.equal(val, 5, "Val should be 2 + 3")
+      test.done()
+    })
+}
+
 // test binding a callback function with a promise
 exports.testBindPromise = function (test) {
   var adder = function (a, b, callback) {