W3cubDocs

/Web APIs

FileSystemSyncAccessHandle: truncate() method

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

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 DOMException: Thrown if the newSize is larger than the original size of the file, and exceeds the browser's storage quota.

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 Standard # api-filesystemsyncaccesshandle-truncate

Browser compatibility

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet
`truncate`	102	102	111	No	88	15.2	109	109	111	74	15.2	21.0
`sync_version`	108	108	111	No	94	16.4	109	109	111	74	16.4	21.0