FileSystemHandle

The FileSystemHandle interface of the File System Access API is an object which represents a file or directory entry. Multiple handles can represent the same entry. For the most part you do not work with FileSystemHandle directly but rather its child interfaces FileSystemFileHandle and FileSystemDirectoryHandle.

Below is a list of interfaces based on the FileSystemHandle interface.

FileSystemFileHandle

Represents a handle to a file entry.

FileSystemDirectoryHandle

Provides a handle to a directory entry.

kind Read only

Returns the type of entry. This is 'file' if the associated entry is a file or 'directory'.

name Read only

Returns the name of the associated entry.

isSameEntry()

Compares two handles to see if the associated entries (either a file or directory) match.

queryPermission()

Queries the current permission state of the current handle.

requestPermission()

Requests read or readwrite permissions for the file handle.

The below code allows the user to choose a file from the file picker and then tests to see whether the handle returned is a file or directory

// store a reference to our file handle
let fileHandle;

async function getFile() {
  // open file picker
  [fileHandle] = await window.showOpenFilePicker();

  if (fileHandle.kind === 'file') {
    // run file code
  } else if (fileHandle.kind === 'directory')
    // run directory code
  }

}

The following asynchronous function returns true if user has granted read or readwrite permissions to the file handle. Permission is requested if not.

// fileHandle is a FileSystemFileHandle
// withWrite is a boolean set to true if write

async function verifyPermission(fileHandle, withWrite) {
  const opts = {};
  if (withWrite) {
    opts.mode = 'readwrite';
  }

  // Check if we already have permission, if so, return true.
  if (await fileHandle.queryPermission(opts) === 'granted') {
    return true;
  }

  // Request permission to the file, if the user grants permission, return true.
  if (await fileHandle.requestPermission(opts) === 'granted') {
    return true;
  }

  // The user did not grant permission, return false.
  return false;
}

The following function compares a single entry with an array of entries, and returns a new array with any matching entries removed.

function removeMatches(fileEntry, entriesArr) {

  let newArr = entriesArr.filter( entry => !fileEntry.isSameEntry(entry) )

  return newArr;
}

• File System Access API
• The File System Access API: simplifying access to local files