It's nice to be able to distinguish error types by classes. But it's a bit tricky to correctly create a custom error class in Node.js, so here is an example.

The example also shows how to add an extra parameter called `extra` that will be stored as a property on the error.

### Usage

``` js
var CustomError = require('./errors/custom-error');

function doSomethingBad() {
  throw new CustomError('It went bad!', 42);
}
```

### Features

* **Name appears once** - less editing if you have to create lots of custom error classes
* **Easy to subclass** - just change the last line to inherit from another custom error class you created
* **Correct stack trace** - no extra stack frames, no double capturing of the stack trace

### Anti-patterns

These are some things that I've seen in other proposed solutions that you should avoid.

* `Error.call(this)` - creates another error object (wasting a bunch of time) and doesn't touch `this` at all
* `Error.captureStackTrace(this, arguments.callee);` - works, but `arguments.callee` is deprecated, so don't use it
* `this.stack = (new Error).stack` - this... I don't even...