var write_buffer = new Uint8Array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]); var read_buffer = new Uint8Array(16); var fs = new Filer.FileSystem('local'); fs.mkdir('/tmp'); fs.open('/tmp/', 'w+', function(error, fd) { if(error) return console.error(error); fs.write(fd, ...); fs.read(fd, ...); }); fs.then( function() { return this.mkdir('/tmp'); } ); var fd = fs.open('/myfile.txt', fs.RW); fd.then( function() { return this.write(write_buffer); } ).then( function(nbytes) { this.seek(-nbytes); return this.read(read_buffer); } ).then( function(nbytes) { console.log(read_buffer); } ); });