# Run Async

[![npm](https://badge.fury.io/js/run-async.svg)](http://badge.fury.io/js/run-async)

Utility method to run a function either synchronously or asynchronously using a series of common patterns. This is useful for library author accepting sync or async functions as parameter. `runAsync` will always run them as an async method, and normalize the multiple signature.

# Installation

```bash
npm install --save run-async
```

# Usage

Here's a simple example print the function results and three options a user can provide a function.

```js
var runAsync = require("run-async");

var printAfter = function (func) {
  var cb = function (err, returnValue) {
    console.log(returnValue);
  };
  runAsync(func, cb)(/* arguments for func */);
};
```

#### Using `this.async`

```js
printAfter(function () {
  var done = this.async();

  setTimeout(function () {
    done(null, "done running with callback");
  }, 10);
});
```

#### Returning a promise

```js
printAfter(function () {
  return new Promise(function (resolve, reject) {
    resolve("done running with promises");
  });
});
```

#### Synchronous function

```js
printAfter(function () {
  return "done running sync function";
});
```

#### Custom done factory

```js
var runAsync = require("run-async");

runAsync(function () {
  var callback = this.customAsync();
  callback(null, a + b);
}, "customAsync")(1, 2);
```

#### Passing context to async method

```js
var runAsync = require("run-async");

runAsync(function () {
  assert(this.isBound);
  var callback = this.async();
  callback(null, a + b);
}).call({ isBound: true }, 1, 2);
```

### runAsync.cb

`runAsync.cb` supports all the function types that `runAsync` does and additionally a traditional **callback as the last argument** signature:

```js
var runAsync = require("run-async");

// IMPORTANT: The wrapped function must have a fixed number of parameters.
runAsync.cb(
  function (a, b, cb) {
    cb(null, a + b);
  },
  function (err, result) {
    console.log(result);
  },
)(1, 2);
```

If your version of node support Promises natively (node >= 0.12), `runAsync` will return a promise. Example: `runAsync(func)(arg1, arg2).then(cb)`

# Licence

Copyright (c) 2014 Simon Boudrias (twitter: @vaxilart)  
Licensed under the MIT license.