FileSystemDirectoryEntry.createReader() - Web APIs 编辑

Experimental

This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The FileSystemDirectoryEntry interface's method createReader() returns a FileSystemDirectoryReader object which can be used to read the entries in the directory.

Syntax

directoryReader = FileSystemDirectoryEntry.createReader();

Parameters

None.

Return value

A FileSystemDirectoryReader object which can be used to read the directory's entries.

Example

This example creates a method called readDirectory(), which fetches all of the entries in the specified FileSystemDirectoryEntry and returns them in an array.

function readDirectory(directory) {
  let dirReader = directory.createReader();
  let entries = [];

  let getEntries = function() {
    dirReader.readEntries(function(results) {
      if (results.length) {
        entries = entries.concat(toArray(results));
        getEntries();
      }
    }, function(error) {
      /* handle error -- error is a FileError object */
    });
  };

  getEntries();
  return entries;
}

This works by creating an internal function, getEntries(), which calls itself recursively to get all the entries in the directory, concatenating each batch to the array. Each iteration, readEntries() is called to get more entries. When it returns an empty array, the end of the directory has beenr reached, and the recursion ends. Once control is returned to readDirectory(), the array is returned to the caller.

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• File and Directory Entries API
• Introduction to the File System API
• FileSystemDirectoryReader
• FileSystemDirectoryEntry
• FileSystemFileEntry
• FileSystemEntry