@jil/args/src/utils/formatValue.ts

A convention based argument parsing and formatting library, with strict validation checks

import {ArgsError} from '../errors';
import {Option, ValueType} from '../types';

export function formatValue(value: ValueType, format?: Option<ValueType>['format']): ValueType {
  let nextValue = value;
  const prevType = typeof nextValue;

  if (typeof format === 'function' && prevType !== 'boolean') {
    nextValue = format(nextValue);

    const nextType = typeof nextValue;

    if (nextType !== prevType) {
      throw new ArgsError('VALUE_INVALID_FORMAT', [prevType, nextType]);
    }
  }

  return nextValue;
}