FileSystemObserver: FileSystemObserver() constructor
Experimental:This is anexperimental technology
Check theBrowser compatibility table carefully before using this in production.
Non-standard: This feature is not standardized. We do not recommend using non-standard features in production, as they have limited browser support, and may change or be removed. However, they can be a suitable alternative in specific cases where no standard option exists.
TheFileSystemObserver() constructor creates a newFileSystemObserver object instance.
Syntax
new FileSystemObserver(callback)Parameters
callbackA user-defined callback function that will be called when the observer has observed a change in the file system entry it has been asked to observe (via
FileSystemObserver.observe()). The callback function will be passed the following two parameters:recordsAn array of
FileSystemChangeRecordobjects that contain details of all the observed changes.observerA reference to the current
FileSystemObserverobject, which is made available in case, for example, you want to stop observations after the current records have been received using theFileSystemObserver.disconnect()method.
Return value
A newFileSystemObserver object.
Examples
Note:For a complete working example, check outFile System Observer Demo (source code).
Initializing aFileSystemObserver
Before you can start observing file or directory changes, you need to initialize aFileSystemObserver to handle the observations:
const observer = new FileSystemObserver(callback);The callback function body can be specified to return and process file change observations in any way you want:
const callback = (records, observer) => { for (const record of records) { console.log("Change detected:", record); const reportContent = `Change observed to ${record.changedHandle.kind} ${record.changedHandle.name}. Type: ${record.type}.`; sendReport(reportContent); // Some kind of user-defined reporting function } observer.disconnect();};Specifications
Not currently part of a specification. Seehttps://github.com/whatwg/fs/pull/165 for the relevant specification PR.
Browser compatibility
See also
- File System API
- The File System Observer API origin trial on developer.chrome.com (2024)