Semitone practice

semitones.js

var readline = require('readline');

var DIFFICULTY = 3; // Min is 1, Max is 11

var rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout
});

var notes = ['A','Bb','B','C','Db','D','Eb','E','F','Gb','G','Ab'];

var askNextNote = function() {
  var randIndex = Math.floor(Math.random() * 12);
  var randNote = notes[randIndex];
  
  var randNext = (Math.floor(Math.random() * DIFFICULTY) % 12) + 1;
  
  var nextIndex = (randIndex + randNext) % 12;
  var nextNote = notes[nextIndex];
  
  var showQ = function() {
    rl.question("What note is " + randNext + " semitones after " + randNote + "? ", function(answer) {
      var a = answer.trim().toLowerCase();
      if(a === nextNote.toLowerCase()) {
        console.log(answer + " is correct");
        askNextNote();
      }
      else if(a === 'exit') {
        console.log("Finished");
        rl.close();
      }
      else {
        console.log("XXX: " + answer + " is incorrect :XXX");
        showQ();
      }
    });
  };
  
  showQ();
};

console.log("The current difficulty is: " + DIFFICULTY);
console.log("The possible notes are: " + notes);
askNextNote();