我正在使用 TypeScript 的 express 在 Firebase 云函數(shù)中實現(xiàn)一個簡單的 WebAPI。我的代碼如下。import * as functions from 'firebase-functions';import * as express from 'express';const app = express()app.post('/', (req, res) => {    var resText: string = "NotEmpty"    const text: string = req.body.text    if (isEmpty(text)) {        resText = "Empty"    }    console.log("text: ", text)    console.log("resText: ", resText)    res.send("Echo " + resText)})exports.api = functions.https.onRequest(app)const isEmpty = (str: string): boolean => {    console.log("str: ", str, "+++")    const trimedStr = str.trim()    const result = (trimedStr === null || trimedStr === "")    console.log("result: ", result)    return result}構(gòu)建以將打字稿轉(zhuǎn)換為 javascript 工作正常。但是，當我執(zhí)行 POST 方法時，發(fā)生了以下錯誤。>  TypeError: Cannot read property 'trim' of undefined>      at isEmpty (/Users/kenny/Test/firebase_functions/functions/lib/index.js:22:27)>      at app.post (/Users/kenny/Test/firebase_functions/functions/lib/index.js:9:9)>      at Layer.handle [as handle_request] (/Users/kenny/Test/firebase_functions/functions/node_modules/express/lib/router/layer.js:95:5)>      at next (/Users/kenny/Test/firebase_functions/functions/node_modules/express/lib/router/route.js:137:13)>      at Route.dispatch (/Users/kenny/Test/firebase_functions/functions/node_modules/express/lib/router/route.js:112:3)>      at Layer.handle [as handle_request] (/Users/kenny/Test/firebase_functions/functions/node_modules/express/lib/router/layer.js:95:5)>      at /Users/kenny/Test/firebase_functions/functions/node_modules/express/lib/router/index.js:281:22>      at Function.process_params (/Users/kenny/Test/firebase_functions/functions/node_modules/express/lib/router/index.js:335:12)>      at next (/Users/kenny/Test/firebase_functions/functions/node_modules/express/lib/router/index.js:275:10)>      at expressInit (/Users/kenny/Test/firebase_functions/functions/node_modules/express/lib/middleware/init.js:40:5)我該如何解決這個錯誤？