# signal-exit

When you want to fire an event no matter how a process exits:

- reaching the end of execution.
- explicitly having `process.exit(code)` called.
- having `process.kill(pid, sig)` called.
- receiving a fatal signal from outside the process

Use `signal-exit`.

```js
// Hybrid module, either works
import { onExit } from 'signal-exit'
// or:
// const { onExit } = require('signal-exit')

onExit((code, signal) => {
  console.log('process exited!', code, signal)
})
```

## API

`remove = onExit((code, signal) => {}, options)`

The return value of the function is a function that will remove
the handler.

Note that the function _only_ fires for signals if the signal
would cause the process to exit. That is, there are no other
listeners, and it is a fatal signal.

If the global `process` object is not suitable for this purpose
(ie, it's unset, or doesn't have an `emit` method, etc.) then the
`onExit` function is a no-op that returns a no-op `remove` method.

### Options

- `alwaysLast`: Run this handler after any other signal or exit
  handlers. This causes `process.emit` to be monkeypatched.

### Browser Fallback

The `'signal-exit/browser'` module is the same fallback shim that
just doesn't do anything, but presents the same function
interface.

Patches welcome to add something that hooks onto
`window.onbeforeunload` or similar, but it might just not be a
thing that makes sense there.