FileSystemFileHandle: createWritable() method
Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.
Note: This feature is available in Web Workers.
The createWritable()
method of the FileSystemFileHandle
interface creates a FileSystemWritableFileStream
that can be used to write to a file.
The method returns a Promise
which resolves to this created stream.
Any changes made through the stream won't be reflected in the file represented by the file handle until the stream has been closed. This is typically implemented by writing data to a temporary file, and only replacing the file represented by file handle with the temporary file when the writable filestream is closed.
Syntax
createWritable()
createWritable(options)
Parameters
options
Optional-
An object with the following properties:
keepExistingData
Optional-
A
Boolean
. Defaultfalse
. When set totrue
if the file exists, the existing file is first copied to the temporary file. Otherwise the temporary file starts out empty.
Return value
A Promise
which resolves to a FileSystemWritableFileStream
object.
Exceptions
NotAllowedError
DOMException
-
Thrown if the
PermissionStatus.state
for the handle is not'granted'
inreadwrite
mode. NotFoundError
DOMException
-
Thrown if current entry is not found.
NoModificationAllowedError
DOMException
-
Thrown if the browser is not able to acquire a lock on the file associated with the file handle.
AbortError
DOMException
-
Thrown if implementation-defined malware scans and safe-browsing checks fails.
Examples
The following asynchronous function writes the given contents to the file handle, and thus to disk.
async function writeFile(fileHandle, contents) {
// Create a FileSystemWritableFileStream to write to.
const writable = await fileHandle.createWritable();
// Write the contents of the file to the stream.
await writable.write(contents);
// Close the file and write the contents to disk.
await writable.close();
}
Specifications
Specification |
---|
File System Standard # api-filesystemfilehandle-createwritable |
Browser compatibility
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