# webwackify

Inspired heavily by [webworkify](https://github.com/browserify/webworkify) and [webworkify-webpack-dropin](https://github.com/Ambroos/webworkify-webpack-dropin)

launch a web worker that can require() in the browser with browserify and webpack

# example

First, a `main.js` file will launch the `worker.js` and print its output:

``` js
var resolveWorker = function() {
  var result;

  try {
    result = require.resolve('./worker.js');
  } catch (e) {}

  return result;
};

var work = require('webworkify');

var w = work(require('./worker.js'), resolveWorker());
w.addEventListener('message', function (ev) {
    console.log(ev.data);
});

w.postMessage(4); // send the worker a message
```

then `worker.js` can `require()` modules of its own.

NOTE: `resolveWorker()` is used because he module id of the worker is required to pass along with the worker when webpack is used to bundle the project. Webpack will resolve module ids at build time by replacing calls to `require.resolve`. Browserify does not do this however, and we have to resolve the module ids ourselves using the dependency graph provided by browserify, so the `try{}catch{}` is added to prevent runtime errors.

The worker function lives
inside of the `module.exports`:

``` js
var gamma = require('gamma');

module.exports = function (self) {
    self.addEventListener('message',function (ev){
        var startNum = parseInt(ev.data); // ev.data=4 from main.js

        setInterval(function () {
            var r = startNum / Math.random() - 1;
            self.postMessage([ startNum, r, gamma(r) ]);
        }, 500);
    });
};
```

Now after [browserifying](http://browserify.org) this example, the console will
contain output from the worker:

```
[ 4, 0.09162078520553618, 10.421030346237066 ]
[ 4, 2.026562457360466, 1.011522336481017 ]
[ 4, 3.1853125018703716, 2.3887589540750214 ]
[ 4, 5.6989969260510005, 72.40768854476167 ]
[ 4, 8.679491643020487, 20427.19357947782 ]
[ 4, 0.8528139834191428, 1.1098187157762498 ]
[ 4, 8.068322137547542, 5785.928308309402 ]
...
```

# methods

``` js
var work = require('webworkify')
```

## var w = work(require(modulePath), moduleId)

Return a new
[web worker](https://developer.mozilla.org/en-US/docs/Web/API/Worker)
from the module at `modulePath`.

The file at `modulePath` should export its worker code in `module.exports` as a
function that will be run with no arguments.

Note that all the code outside of the `module.exports` function will be run in
the main thread too so don't put any computationally intensive code in that
part. It is necessary for the main code to `require()` the worker code to fetch
the module reference and load `modulePath`'s dependency graph into the bundle
output.

`moduleId` is required when bundling with webpack. You can get the `moduleId` by calling `require.resolve(modulePath)`. It is suggested to use a `resolveWorker()` function like in the above example to avoid runtime errors when bundled with browserify.

``` js
var resolveWorker = function() {
  var result;

  try {
    result = require.resolve(modulePath);
  } catch (e) {}

  return result;
};
```

## Worker.objectURL

The worker `w` returned by `webworkify` has the property `objectURL` attached.
`w.objectURL` refers to the Object URL that was used to pass the module's source
to the worker, and can be cleaned up using `URL.revokeObjectURL()`.  (See [example](https://github.com/substack/webworkify/blob/master/example/main.js))

# install

With [npm](https://npmjs.org) do:

```
npm install webwackify
```

# license

MIT