试试这样：

JSON.parse(jsonString, (key, value) => {

   if (!isNaN(value)) {
      return Number(value);
   }

   return value;
});

仅当值表示数字时，才转换为数字

这是没有意义的JSON.stringify只是JSON.parse它再次。在typescript playground上验证此示例-

type t_card = {
  sub_type: number
  year: number
  peak: string
}

type t_serialized_card = {
  sub_type: string
  year: string
  peak: string
}

function stringToNumberExn(s: string): number {
  const n = Number.parseInt(s)
  if (Number.isNaN(n))
    throw Error(`stringToNumberExn: ${s} is not a number`)
  return n
}

async function getCards(): Promise<Array<t_card>> {
  // format as returned from backend
  const res: Array<t_serialized_card> = 
    await fetch("/path/to/cards").then(r => r.json())

  // map to desired format 
  return res.map(card => ({
    sub_type: stringToNumberExn(card.sub_type),
    year: stringToNumberExn(card.year),
    peak: card.peak
  }))
}