FileSystemSyncAccessHandle: getSize() method
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since March 2023.
Secure context: This feature is available only insecure contexts (HTTPS), in some or allsupporting browsers.
Note: This feature is only available inDedicated Web Workers.
ThegetSize() method of theFileSystemSyncAccessHandle interface returns the size of the file associated with the handle in bytes.
Note:In earlier versions of the spec,close(),flush(),getSize(), andtruncate() were wrongly specified as asynchronous methods, and older versions of some browsers implement them in this way. However, all current browsers that support these methods implement them as synchronous methods.
Syntax
getSize()Parameters
None.
Return value
A number representing the size of the file in bytes.
Exceptions
InvalidStateErrorDOMExceptionThrown if the associated access handle is already closed.
Examples
The following asynchronous event handler function is contained inside a Web Worker. On receiving a message from the main thread it:
- Creates a synchronous file access handle.
- Gets the size of the file and creates an
ArrayBufferto contain it. - Reads the file contents into the buffer.
- Encodes the message and writes it to the end of the file.
- Persists the changes to disk and closes the access handle.
onmessage = async (e) => { // Retrieve message sent to work from main script const message = e.data; // Get handle to draft file const root = await navigator.storage.getDirectory(); const draftHandle = await root.getFileHandle("draft.txt", { create: true }); // Get sync access handle const accessHandle = await draftHandle.createSyncAccessHandle(); // Get size of the file. const fileSize = accessHandle.getSize(); // Read file content to a buffer. const buffer = new DataView(new ArrayBuffer(fileSize)); const readBuffer = accessHandle.read(buffer, { at: 0 }); // Write the message to the end of the file. const encoder = new TextEncoder(); const encodedMessage = encoder.encode(message); const writeBuffer = accessHandle.write(encodedMessage, { at: readBuffer }); // Persist changes to disk. accessHandle.flush(); // Always close FileSystemSyncAccessHandle if done. accessHandle.close();};Specifications
| Specification |
|---|
| File System # api-filesystemsyncaccesshandle-getsize |