<p>我正在嘗試為我的函數定義輸出類型，我想根據<code>toNumberIfNeeded</code>標誌在<code>string</code>和<code>number<code>string</code>和<code>number<code>類型之間設定條件，假設如果<code>toNumberIfNeeded</code>為真，則此函數將傳回一個數字類型，反之傳回字串類型。我該如何做？ </p> <pre class="brush:php;toolbar:false;">interface Options { uppercase?: boolean; filterSpecialChars?: boolean; toNumberIfNeeded?: boolean; } export const textTransformer = (text: string, options?: Options) => { const { uppercase, filterSpecialChars, toNumberIfNeeded} = options || {}; // 我的處理邏輯程式碼 return toNumberIfNeeded ? parseInt(text) : text; }</pre> <p>預期的範例：</p> <pre class="brush:php;toolbar:false;">textTransformer('hello'); // 傳回字串類型 textTransformer('123', { toNumberIfNeeded: true }); // 回傳數字型別</pre>

interface Options {
  uppercase: boolean;
  filterSpecialChars: boolean;
  toNumberIfNeeded: boolean;
}

export const textTransformer = <T extends Options>(
  text: string,
  options?: T
): T["toNumberIfNeeded"] extends true ? number : string => {
  const {uppercase, filterSpecialChars, toNumberIfNeeded} =
    options || {};
  // 我的处理逻辑代码

  return (toNumberIfNeeded ? parseInt(text) : text) as ReturnType<
    typeof textTransformer
  >;
};

textTransformer("hello"); // 推断为 string
textTransformer("123", {
  toNumberIfNeeded: true,
  uppercase: false,
  filterSpecialChars: false
}); // 推断为 number