YuxiUx

JS

function noteToFreq(note) {
    let a = 440; //frequency of A (coomon value is 440Hz)
    return (a / 32) * (2 ** ((note - 9) / 12));
}

PHP

function noteToFreq($note) {

xposedbones

Number.prototype.map = function (in_min, in_max, out_min, out_max) {
  return (this - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
}

borismus

var BASE64_MARKER = ';base64,';

function convertDataURIToBinary(dataURI) {
  var base64Index = dataURI.indexOf(BASE64_MARKER) + BASE64_MARKER.length;
  var base64 = dataURI.substring(base64Index);
  var raw = window.atob(base64);
  var rawLength = raw.length;
  var array = new Uint8Array(new ArrayBuffer(rawLength));

  for(i = 0; i < rawLength; i++) {