code: function $cond(params) {
      if (
          Array.isArray(params) &&
          params.length === 3 &&
          typeof params[0] === 'boolean'
      ) {
          return params[0] ? params[1] : params[2];
      }
      throw new Error(
          '$cond expects an array of three elements of which the first must be a boolean'
      );
  }
docs: Return the second or third element based on the boolean value of the first element
  
  @param {[boolean, any, any]} params
  @returns {any}