JSFiddle - React, Tailwind, and code Playground

JavaScript

function Range(start, end)
{
  var result = [];
  if ($.isNumeric(start) && $.isNumeric(end))
  {
    result = new Array(end - start + 1).fill().map((d, i) => i + start);
  } else
    {
      var arr = new Array(end.charCodeAt() - start.charCodeAt() + 1).fill().map((d, i) => String.fromCharCode(i + start.charCodeAt())),
      str = String(arr);
      if ((/[А-Яё]/gi).test(str)) RegExp = (/[А-Яё]/gi);
      if ((/[A-Z]/gi).test(str)) RegExp = (/[A-Z]/gi);
      result = str.match(RegExp);
    }
  return result;
}
function UnicodeParse(arr, str)
{
  var result = [];
  for (var i = 0; i < arr.length; i++)
  {
    var a = arr[i];
    if ($.isNumeric(arr[0]))
    {
      if (str == 'cod')
      {
        result[i] = String.fromCharCode(a);
      }
      if (str == 'arr')
      {
        result[a] = String.fromCharCode(a);
      }
    } else
      {
        if (str == 'cod')
        {
          result[i] = a.charCodeAt();
        }
        if (str == 'arr')
        {
          result[a] = a.charCodeAt();
        }
      }
  }
  return result;
}

console.log(Range(72, 79));
console.log(UnicodeParse(Range(72, 79), 'cod'));
console.log(UnicodeParse(Range(72, 79), 'arr'));

console.log(Range('A', 'z'));
console.log(UnicodeParse(Range('A', 'z'), 'cod'));
console.log(UnicodeParse(Range('A', 'z'), 'arr'));

console.log(Range('Ё', 'ё'));
console.log(UnicodeParse(Range('Ё', 'ё'), 'cod'));
console.log(UnicodeParse(Range('Ё', 'ё'), 'arr'));