TypeScript: Unit Conversion Class

gistfile1.txt

/**
 * Convert from units to another units e.g. from square feet to acres
 * return original value if conversion units are not supported
 * Usage:
 *   const convertedValue = convert(100).from('acres').to('square feet');
 * expected: 
 *   4356000
 */
class Converter {
  private toUnits: string;
  private fromUnits: string;
  private convertedValue: number;

  constructor(private value: string) {
    this.convertedValue = Number(value);
  }

  public to(units: string, fractionDigits: number = 0): string {
    this.toUnits = units.toLowerCase();

    if (this.toUnits === 'square feet' && this.fromUnits === 'acres') {
      this.convertedValue = this.convertedValue * 43560;
    } else if (this.toUnits === 'acres' && this.fromUnits === 'square feet') {
      this.convertedValue = this.convertedValue / 43560;
    } else {
      // return original value
      return this.value;
    }

    return this.convertedValue.toFixed(fractionDigits);
  }

  public from(units: string): Converter {
    this.fromUnits = units.toLowerCase();

    return this;
  }
}

export const convert = (value: string) => {
  return new Converter(value);
};