watchpack high level API doesn't map directly to watchers. Instead a three level architecture ensures that for each directory only a single watcher exists.
- The high level API requests `DirectoryWatchers` from a `WatcherManager`, which ensures that only a single `DirectoryWatcher` per directory is created.
- A user-faced `Watcher` can be obtained from a `DirectoryWatcher` and provides a filtered view on the `DirectoryWatcher`.
- Reference-counting is used on the `DirectoryWatcher` and `Watcher` to decide when to close them.
- The real watchers are created by the `DirectoryWatcher`.
- Files are never watched directly. This should keep the watcher count low.
- Watching can be started in the past. This way watching can start after file reading.
- Symlinks are not followed, instead the symlink is watched.
## API
```javascript
var Watchpack = require("watchpack");
var wp = new Watchpack({
// options:
aggregateTimeout: 1000,
// fire "aggregated" event when after a change for 1000ms no additional change occurred
// aggregated defaults to undefined, which doesn't fire an "aggregated" event
poll: true,
// poll: true - use polling with the default interval
// poll: 10000 - use polling with an interval of 10s
// poll defaults to undefined, which prefer native watching methods
// Note: enable polling when watching on a network path
// When WATCHPACK_POLLING environment variable is set it will override this option
followSymlinks: true,
// true: follows symlinks and watches symlinks and real files
// (This makes sense when symlinks has not been resolved yet, comes with a performance hit)
// false (default): watches only specified item they may be real files or symlinks
// (This makes sense when symlinks has already been resolved)
ignored: "**/.git"
// ignored: "string" - a glob pattern for files or folders that should not be watched
// ignored: ["string", "string"] - multiple glob patterns that should be ignored
// ignored: /regexp/ - a regular expression for files or folders that should not be watched
// ignored: (entry) => boolean - an arbitrary function which must return truthy to ignore an entry
// For all cases expect the arbitrary function the path will have path separator normalized to '/'.
// All subdirectories are ignored too
});
// Watchpack.prototype.watch({
// files: Iterable<string>,
// directories: Iterable<string>,
// missing: Iterable<string>,
// startTime?: number
// })
wp.watch({
files: listOfFiles,
directories: listOfDirectories,
missing: listOfNotExistingItems,
startTime: Date.now() - 10000
});
// starts watching these files and directories
// calling this again will override the files and directories
// files: can be files or directories, for files: content and existence changes are tracked
// for directories: only existence and timestamp changes are tracked
// directories: only directories, directory content (and content of children, ...) and
// existence changes are tracked.
// assumed to exist, when directory is not found without further information a remove event is emitted
// missing: can be files or directorees,
// only existence changes are tracked
// expected to not exist, no remove event is emitted when not found initially
// files and directories are assumed to exist, when they are not found without further information a remove event is emitted
// missing is assumed to not exist and no remove event is emitted
