FileSystemDirectoryEntry: createReader() method
  The FileSystemDirectoryEntry interface's method
  createReader() returns a
  FileSystemDirectoryReader object which can be used to read the entries in
  the directory.
Syntax
js
createReader()
Parameters
None.
Return value
  A FileSystemDirectoryReader object which can be used to read the
  directory's entries.
Examples
  This example creates a method called readDirectory(), which fetches all of
  the entries in the specified FileSystemDirectoryEntry and returns them in
  an array.
js
function readDirectory(directory) {
  let dirReader = directory.createReader();
  let entries = [];
  let getEntries = () => {
    dirReader.readEntries(
      (results) => {
        if (results.length) {
          entries = entries.concat(toArray(results));
          getEntries();
        }
      },
      (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 been reached, and the recursion ends. Once control is returned
  to readDirectory(), the array is returned to the caller.
Specifications
| Specification | 
|---|
| File and Directory Entries API # dom-filesystemdirectoryentry-createreader | 
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