How to use the json-6.begin function in json-6

function preloadDisk( opt, disk ) {
		if( fileState.loaded )
			return; // already have the disk image in memory
		if( fileState.flushPending || fileState.writing ) {
			_debug && console.log( "wait for pending flush on another connection?" );
			setTimeout( ()=>preloadDisk( opt, disk ), fileDelay/3 );
			return;
		}
		fileState.reading = true;
		_debug && console.log( new Date(), "preload happened." );
		const stream = fs.createReadStream( fileName, { flags:"r", encoding:"utf8"} );
		const parser = json6.begin( function(val) {
			//_json_debug && console.log( "Recover:", val[0] );
			disk[val[0]] = val[1];
		} );
		stream.on('open', function() {
			_debug && console.log( new Date(), "Read stream opened.." );
		} );
		stream.on('error', function( err ){ 
			if( err.code !== 'ENOENT' )
				console.log( "READ STREAM ERROR:", err );
			loaded = true;
			fileState.reading = false;
			handlePending();
		} );
 	 	stream.on('data', function(chunk) {
			//_json_debug && console.log( "got stream data",chunk );
			parser.write( chunk );