centsOffPitch.js

var findCentsOffPitch = function(freq, refFreq) {
    // We need to find how far freq is from baseFreq in cents
    var log2 = 0.6931471805599453; // Math.log(2)
    var multiplicativeFactor = freq / refFreq;
    
    // We use Math.floor to get the integer part and ignore decimals
    var cents = Math.floor(1200 * (Math.log(multiplicativeFactor) / log2));
    return cents;
};