FileSystemWritableFileStream
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The FileSystemWritableFileStream interface of the File System Access API is a WritableStream object with additional convenience methods, which operates on a single file on disk. The interface is accessed through the FileSystemFileHandle.createWritable() method.
Instance properties
Inherits properties from its parent, WritableStream.
Instance methods
Inherits methods from its parent, WritableStream.
FileSystemWritableFileStream.write-
Writes content into the file the method is called on, at the current file cursor offset.
FileSystemWritableFileStream.seek-
Updates the current file cursor offset to the position (in bytes) specified.
FileSystemWritableFileStream.truncate-
Resizes the file associated with the stream to be the specified size in bytes.
Examples
This asynchronous function opens the 'Save File' picker, which returns a FileSystemFileHandle once a file is selected. From which a writable stream is then created using the FileSystemFileHandle.createWritable() method.
A user defined Blob is then written to the stream which is subsequently closed.
js
async function saveFile() {
// create a new handle
const newHandle = await window.showSaveFilePicker();
// create a FileSystemWritableFileStream to write to
const writableStream = await newHandle.createWritable();
// write our file
await writableStream.write(imgBlob);
// close the file and write the contents to disk.
await writableStream.close();
}
The following show different examples of options that can be passed into the write() method.
js
// just pass in the data (no options)
writableStream.write(data);
// writes the data to the stream from the determined position
writableStream.write({ type: "write", position, data });
// updates the current file cursor offset to the position specified
writableStream.write({ type: "seek", position });
// resizes the file to be size bytes long
writableStream.write({ type: "truncate", size });
Specifications
| Specification |
|---|
| File System Standard # api-filesystemwritablefilestream |
Browser compatibility
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