An asynchronous utility method for calculating percentages to a given precision

calculatePercentage.ts

  /**
   * 
   * Asynchronously calculate a percentage to a given precision.
   * @example
   * const denominator: number = 435;
   * const numberator: number = 37;
   * const precision: number = 2;
   * const percentage: number = await calculatePercentage(denominator, numerator, precision);
   * console.log(`${numerator} is ${percentage} percent of ${denominator} to a precision of ${precision}`);
   * @param {string|number} denominator - The value that the percentage will modify.
   * @param {string|number} numerator - The result of the percentage operating on the denominator .
   * @param {number} [precision=2] - The precision by which to calculate the percentage, which is the number of decimal places. 
   * @returns {Promise<number>} Thenable/Awaitable percentage
   */
  export const calculatePercentage = async (denominator: string | number, numerator: string | number, precision: number = 2): Promise<number> => {
    try {
      // Copy parameters to temp parameters so that we can pass them back as they were sent to us in any applicable error message - such as before they are converted to floats or ints
      const __numerator: any = numerator;
      const __denominator: any = denominator;
      const __precision: any = precision;

      let percentage: number;

      numerator = numerator ? (typeof numerator === 'string' ? parseFloat(numerator) : numerator) : 0;
      denominator = denominator ? (typeof denominator === 'string' ? parseFloat(denominator) : denominator) : 0;
      if (isNaN(numerator) || isNaN(denominator) || isNaN(precision)) throw ({code: 'NOTANUMBER', debug: {numerator: __numerator, numeratorType: typeof __numerator, denominator: __denominator, denominatorType: typeof __denominator, precision: __precision, precisionType: typeof __precision}, message: 'One or more parameters was not a number'});
      
      if (numerator === denominator) {
        percentage = 0;
      } else {
        percentage = parseFloat(((denominator / numerator) * 100).toPrecision(precision));
      }

      if (percentage === Infinity || percentage === -Infinity) {
        percentage = 0;
      }

      if (isNaN(percentage)) throw ({code: 'NOTANUMBER', debug: {percentage: percentage, percentageType: typeof percentage}, message: 'Percentage value calculated to not a number'});
      return Promise.resolve(percentage);
    } catch (error) {
      return Promise.reject(error);
    }
  }