Simple, yet elegant python like string count

count.ts

export default function count(
  str: string,
  {
    trim,
    strict,
    custom,
  }: {
    trim?: boolean
    strict?: boolean
    custom?: RegExp
  }
): number {
  const regex = RegExp

  let result = 0
  let spaces = regex(/[\s/\t]/gi)
  let alphanumeric = regex(
    /[~`!@#$₺%^&*¡™£¢∞§¶•ªº–≠«‘“()_+|}{'":;\/?.>,<œ∑´®†¥¨ˆøπåß∂ƒ©˙∆˚¬µ˜∫√≈\{\}\[\]\\\/\s/\t]/gi
  )

  if (trim) {
    str = str.replace(spaces, '')
  }

  if (strict) {
    str = str.replace(alphanumeric, '')
    console.info(
      'count function only handles alphanumeric characters when strict option is selected'
    )
  }

  if (custom?.source.length) {
    if (strict) {
      throw new Error(
        'count function can not execute custom expression when strict option is selected.'
      )
    }

    if (!(custom instanceof regex)) {
      throw new Error('count function custom option must be a Regular Expression!')
    }

    if (regex(custom).test(str)) {
      str = str.replace(custom, '')
    }
  }

  for (let i = 0; i < str.length; i++) {
    result = +(i + 1)
  }

  return result
}

const c = count('Lorem ipsum dolor sit amet.', {
  trim: true,
})

console.log(c)