magicFunction.js

function adjustFreqData(shapeNo) {
  analyserNode.getByteFrequencyData(frequencyData);
  var removed = frequencyData.slice(0,1024);
  
  var newFreqs = [], prevRangeStart = 0, prevItemCount = 0;

  // set up the maxPow & thus ratio based on shapeCount
  var maxPow = Math.pow(2,shapeNo/2);
  var ratio = 1024/maxPow;
  
  // looping - get values for new array based on shapeCount
  for (let j=1; j<shapeNo+1; j++) {
    var itemCount, rangeStart;

    var pow = j/2;

    // use ratio to get itemCount (round)
    itemCount = Math.ceil( ((Math.pow(2, pow))*ratio)/2 );

    rangeStart = prevRangeStart + Math.ceil(prevItemCount/2);
     // get new values
    var newValue = 0, total = 0;
    for (let k=rangeStart; k<rangeStart+itemCount; k++) {
      // add up items and divide by total
      total += frequencyData[k];
      newValue = parseInt(total/itemCount);
    }
    // add to new array
    newFreqs.push(newValue);

    prevItemCount = itemCount;
    prevRangeStart = rangeStart;
  }
  
  return newFreqs;
}