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FileSystemSyncAccessHandle: truncate() method

Baseline 2023

Newly available

Since ⁨March 2023⁩, this feature works across the latest devices and browser versions. This feature might not work in older devices or browsers.

Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.

Note: This feature is only available in Dedicated Web Workers.

The truncate() method of the FileSystemSyncAccessHandle interface resizes the file associated with the handle to a specified number of bytes.

Note: In earlier versions of the spec, close(), flush(), getSize(), and truncate() 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

truncate(newSize)

Parameters

newSize: The number of bytes to resize the file to.

Return value

None (undefined).

Exceptions

InvalidStateError DOMException: Thrown if the associated access handle is already closed, or if the modification of the file's binary data otherwise fails.
QuotaExceededError: Thrown if the newSize is larger than the original size of the file, and exceeds the browser's storage quota.
TypeError: Thrown if the underlying file system does not support setting the file size to the new size.

Examples

async function truncateFile() {
  // 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();

  // Truncate the file to 0 bytes
  accessHandle.truncate(0);

  // Persist changes to disk.
  accessHandle.flush();

  // Always close FileSystemSyncAccessHandle if done.
  accessHandle.close();
}

Specifications

Specification
File System> # api-filesystemsyncaccesshandle-truncate>

Browser compatibility

	Desktop					Mobile
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet	WebView Android	WebView on iOS
`truncate`	102	102	111	88	15.2	109	111	74	15.2	21.0	109	15.2
`sync_version`	108	108	111	94	16.4	109	111	74	16.4	21.0	109	16.4