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# watchpack
Wrapper library for directory and file watching.
[](https://github.com/webpack/watchpack/actions/workflows/test.yml)[](https://codecov.io/gh/webpack/watchpack)[](https://www.npmjs.com/package/watchpack)
## Concept
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
```javascriptvar 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 directories,// 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
wp.on("change", function(filePath, mtime, explanation) { // filePath: the changed file // mtime: last modified time for the changed file // explanation: textual information how this change was detected});
wp.on("remove", function(filePath, explanation) { // filePath: the removed file or directory // explanation: textual information how this change was detected});
wp.on("aggregated", function(changes, removals) { // changes: a Set of all changed files // removals: a Set of all removed files // watchpack gives up ownership on these Sets.});
// Watchpack.prototype.pause()wp.pause();// stops emitting events, but keeps watchers open// next "watch" call can reuse the watchers// The watcher will keep aggregating events// which can be received with getAggregated()
// Watchpack.prototype.close()wp.close();// stops emitting events and closes all watchers
// Watchpack.prototype.getAggregated(): { changes: Set<string>, removals: Set<string> }const { changes, removals } = wp.getAggregated();// returns the current aggregated info and removes that from the watcher// The next aggregated event won't include that info and will only emitted// when futher changes happen// Can also be used when paused.
// Watchpack.prototype.collectTimeInfoEntries(fileInfoEntries: Map<string, Entry>, directoryInfoEntries: Map<string, Entry>)wp.collectTimeInfoEntries(fileInfoEntries, directoryInfoEntries);// collects time info objects for all known files and directories// this include info from files not directly watched// key: absolute path, value: object with { safeTime, timestamp }// safeTime: a point in time at which it is safe to say all changes happened before that// timestamp: only for files, the mtime timestamp of the file
// Watchpack.prototype.getTimeInfoEntries()var fileTimes = wp.getTimeInfoEntries();// returns a Map with all known time info objects for files and directories// similar to collectTimeInfoEntries but returns a single map with all entries
// (deprecated)// Watchpack.prototype.getTimes()var fileTimes = wp.getTimes();// returns an object with all known change times for files// this include timestamps from files not directly watched// key: absolute path, value: timestamp as number```
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