Gasでgoogle translateを自動言語検知ありで使えるやつです

gas.js

function translate(text, from = "auto", to) {
  try {
    const result = UrlFetchApp.fetch(
      "https://translate.google.com/_/TranslateWebserverUi/data/batchexecute",
      {
        payload:
          "f.req=" +
          encodeURIComponent(
            JSON.stringify([
              [
                [
                  "MkEWBc",
                  `[[\"${text}\",\"${from}\",\"${to}\",true],[null]]`,
                  null,
                  "generic",
                ],
              ],
            ])
          ),
      }
    ).getContentText();
    return JSON.parse(
      JSON.parse(result.split("\n").slice(2)[0])[0][2]
    )[1][0][0][5][0][0];
  } catch {
    return "";
  }
}

function createResponse(payload) {
  return ContentService.createTextOutput()
    .setMimeType(ContentService.MimeType.JSON)
    .setContent(payload);
}

function doGet(event) {
  const { text, from, to } = event.parameter;
  if (!text || !to) return createResponse("");
  const result = translate(text, from, to);
  return createResponse(result);
}