const fs = require('fs'); const { MidiFile,YJKFile,YJKFileConverter } = require('@kmoon2437/midifile'); let midi = fs.readFileSync('...'); // your midi file. it can be an ArrayBuffer or Uint8Array or nodejs Buffer let file = new MidiFile(midi); // MidiFile instance file.header.format; // 0,1 or 2 file.header.ticksPerBeat; // If division is frames per seconds, this is null file.header.tickResolution; // microseconds per tick file.header.tracksCount; // n file.header.durationTick; // duration in tick file.header.durationMs; // duration in ms file.tracks; // array file.tempoEvents; // "set tempo" events let yjk = fs.readFileSync('...'); // your yjk file. it can be an ArrayBuffer or Uint8Array or nodejs Buffer let file2 = new YJKFile(yjk); // YJKFile instance file2.header; // similar to MidiFile.header file2.globalEvents; // global events file2.tempoEvents; // "set tempo" events file2.ports; // array let midi2 = fs.readFileSync('...'); // your midi file. it can be an ArrayBuffer or Uint8Array or nodejs Buffer fs.writeFileSync('./test.yjk',YJKFileConverter.midi2yjk(midi2)); // write yjk file