​

  const library = function (text: string) {

    interface ValueObject {

      addQuotes?: Function

    }

​

    const options: ValueObject = {}

​

    options.addQuotes = function () {

      if (!text) return ''

      return `"${text}"`

    }

​

    return options

  }

​

  const result = library('test').addQuotes()

  console.log(result)

​