Compute musical note from arbitrary scale

compute-note.js

export function computeNote(
    // how far from the base note to go in either direction
    distance = 0,
    scale = {
      // use this frequency as basis
      // standard A4 is 440hz
      base: 440.0,
      // claim that its in the 4 repetition of made up sequence,
      // on a normal piano it is saying this is A4
      position: 4,
      // the scale will be divided by the number of notes
      // which also have some arbitrary name like a b c
      // on a normal piano these are 12 semi tones
      notes: ["A", "A#", "B", "C", "C#", "D", "D#", "E", "F", "F#", "G", "G#"],
      // the power tells what the value of the frequency should
      // be after 1 repletion of the sequence.
      // on a normal piano the frequency doubles (power of 2)
      // I.E. A3 = 220hz, A4 = 440hz, A5 = 880hz
      powerOf: 2
    }
  ) {
    const scalar = scale.notes.length;
    const loc = distance / scalar;
    const offset = Math.floor(loc);
    const freq = scale.base * Math.pow(scale.powerOf, loc);
    const note = scale.notes[distance - offset * scalar];
    const position = offset + scale.position;
    return { position, note, freq };
  }