percentage.js

  switch (operation) {
    case "fromPercentage": // what is 5% of 20 ? 1
      var totalValue = a / 100 * b;
      break;
    case "toPercenrage": // 25 is what percent of 50 ? 50%
      var totalValue = a / b * 100;
      break;
    case "diffPercentage": // from 20 to 50 ? 150%
      var totalValue = (b - a) / a * 100;
      break;
  }