function read() {
	var fpath;
	var files;
	var stats;
	var out;
	var f;
	var i;

	files = readDir( dataDir );
	out = [];
	for ( i = 0; i < files.length; i++ ) {
		f = files[ i ];
		if ( extname( f ) === '.json' && RE.test( f ) ) {
			fpath = join( dataDir, f );
			stats = fs.statSync( fpath ); // eslint-disable-line node/no-sync
			if ( stats.isFile() ) {
				out.push( f );
			}
		}
	}
	return out.sort();
}
Generates a sorted list of JSON data file filenames by reading the file system.

@private
@returns {StringArray} filenames