glob-watcher/README.md

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# glob-watcher

[![NPM version][npm-image]][npm-url] [![Downloads][downloads-image]][npm-url] [![Build Status][travis-image]][travis-url] [![AppVeyor Build Status][appveyor-image]][appveyor-url] [![Coveralls Status][coveralls-image]][coveralls-url] [![Gitter chat][gitter-image]][gitter-url]

Watch globs and execute a function upon change, with intelligent defaults for debouncing and queueing.

## Example

```js
var watch = require('glob-watcher');

watch(['./*.js', '!./something.js'], function(done){
  // This function will be called each time a globbed file is changed
  // but is debounced with a 200ms delay (default) and queues subsequent calls

  // Make sure to signal async completion with the callback
  // or by returning a stream, promise, observable or child process
  done();

  // if you need access to the `path` or `stat` object, listen
  // for the `change` event (see below)

  // if you need to listen to specific events, use the returned
  // watcher instance (see below)
});

// Raw chokidar instance
var watcher = watch(['./*.js', '!./something.js']);

// Listen for the 'change' event to get `path`/`stat`
// No async completion available because this is the raw chokidar instance
watcher.on('change', function(path, stat) {
  // `path` is the path of the changed file
  // `stat` is an `fs.Stat` object (not always available)
});

// Listen for other events
// No async completion available because this is the raw chokidar instance
watcher.on('add', function(path, stat) {
  // `path` is the path of the changed file
  // `stat` is an `fs.Stat` object (not always available)
});
```

## API

### `watch(globs[, options][, fn])`

Takes a path string, an array of path strings, a [glob][node-glob] string or an array of [glob][node-glob] strings as `globs` to watch on the filesystem. Also optionally takes `options` to configure the watcher and a `fn` to execute when a file changes.

Returns an instance of [chokidar][chokidar].

#### `fn([callback])`

If the `fn` is passed, it will be called when the watcher emits a `change`, `add` or `unlink` event. It is automatically debounced with a default delay of 200 milliseconds and subsequent calls will be queued and called upon completion. These defaults can be changed using the `options`.

The `fn` is passed a single argument, `callback`, which is a function that must be called when work in the `fn` is complete. Instead of calling the `callback` function, [async completion][async-completion] can be signalled by:
  * Returning a `Stream` or `EventEmitter`
  * Returning a `Child Process`
  * Returning a `Promise`
  * Returning an `Observable`

Once async completion is signalled, if another run is queued, it will be executed.

#### `options`

##### `options.ignoreInitial`

If set to `false` the `fn` is called during [chokidar][chokidar] instantiation as it discovers the file paths. Useful if it is desirable to trigger the `fn` during startup.

__Passed through to [chokidar][chokidar], but defaulted to `true` instead of `false`.__

Type: `Boolean`

Default: `true`

##### `options.delay`

The delay to wait before triggering the `fn`. Useful for waiting on many changes before doing the work on changed files, e.g. find-and-replace on many files.

Type: `Number`

Default: `200` (milliseconds)

##### `options.queue`

Whether or not a file change should queue the `fn` execution if the `fn` is already running. Useful for a long running `fn`.

Type: `Boolean`

Default: `true`

##### other

Options are passed directly to [lodash.debounce][lodash-debounce] and [chokidar][chokidar], so all their options are supported. Any debounce-related options are documented in [lodash.debounce][lodash-debounce]. Any chokidar-related options are documented in [chokidar][chokidar].

## License

MIT

[downloads-image]: http://img.shields.io/npm/dm/glob-watcher.svg
[npm-url]: https://npmjs.com/package/glob-watcher
[npm-image]: http://img.shields.io/npm/v/glob-watcher.svg

[travis-url]: https://travis-ci.org/gulpjs/glob-watcher
[travis-image]: http://img.shields.io/travis/gulpjs/glob-watcher.svg?label=travis-ci

[appveyor-url]: https://ci.appveyor.com/project/gulpjs/glob-watcher
[appveyor-image]: https://img.shields.io/appveyor/ci/gulpjs/glob-watcher.svg?label=appveyor

[coveralls-url]: https://coveralls.io/r/gulpjs/glob-watcher
[coveralls-image]: http://img.shields.io/coveralls/gulpjs/glob-watcher/master.svg

[gitter-url]: https://gitter.im/gulpjs/gulp
[gitter-image]: https://badges.gitter.im/gulpjs/gulp.png

[glob]: https://github.com/isaacs/node-glob
[async-completion]: https://github.com/gulpjs/async-done#completion-and-error-resolution
[chokidar]: https://github.com/paulmillr/chokidar
[lodash-debounce]: https://lodash.com/docs#debounce