Can I append plugin output to an existing file?

In the ObjectExplorer plugin I see a mechanism to send output to a NotePad file via:

var rc = outfile.write(output);
if (rc){
console.log("Log file has been written to "+outfile.source);
proc.start("notepad "+outfile.source); // Windows
} else {
console.log("Something went wrong. File cannot be written");
}

Is there a way to append output to an existing outfile?

var rc = outfile.append(output); is not recognized.

Why? I wrote a plugin to record notes and chord symbols from lead sheets, and it would be handy if I could concatenate the results (the album feature again...)