Express - 错误：未指定默认引擎且未提供扩展

Question

我无法让我的 api 与我的快速服务器一起工作，我总是收到一个错误：

错误：未指定默认引擎且未提供扩展。

我很确定它来自快速路由器，但我找不到错误来自哪里......

我是否正确使用了快速路由器？因为我以前从未使用过它。

服务器.js：

const createError = require('http-errors');
const express = require("express");
const bodyParser = require("body-parser");
const cookieParser = require('cookie-parser');
const logger = require('morgan');
const api = require('./routes/api');
const app = express();
const MongoClient = require('mongodb').MongoClient;

const MONGODB_URI = process.env.MONGODB_URI;
const PORT = process.env.PORT || 5000;

app.use('/', api);

app.use(logger('dev'));

app.use(bodyParser.json());

app.use(bodyParser.urlencoded({ extended: true }));
app.use(cookieParser());

// catch 404 and forward to error handler
app.use(function(req, res, next) {
    next(createError(404));
});

// error handler
app.use(function(err, req, res, next) {
    // set locals, only providing error in development
    res.locals.message = err.message;
    res.locals.error = req.app.get('env') === 'development' ? err : {};

    // render the error page
    res.status(err.status || 500);
    res.render('error');
});

// Database object
var db;

// Initialize connection once with db
MongoClient.connect(MONGODB_URI, function(err, database) {
    if(err) throw err;

    db = database;

    // Start the application after the database connection is ready
    app.listen(PORT, () => console.log(`Server listening on port ${PORT}`));
});

module.exports = db;
module.exports = app;

路线/api.js：

// const app = require("../server");
var db = require("../server");
const { videos } = require("../helpers/videos");
const { videoLinksValidator } = require("../helpers/video-links-validator");
const { getTitleType } = require("../helpers/title-type-extractor");
const express = require('express');
const router = express.Router();

router.get('/', (req, res) => {
    console.log("RESPONSE", res) 
});

// Create a GET route
router.get("/express_backend", (req, res) => {
    res.send({ express: "YOUR EXPRESS BACKEND IS CONNECTED TO REACT" });
});

router.post("/video_url", async (req, res)=> {
    const videoURL = req.body.videoURL.videoURL;

    let titleType = await getTitleType(videoURL);

    let videosAndTitle = await videos(videoURL, titleType);

    let videoAndTitleReady = await videoLinksValidator(videosAndTitle);
    console.log(videoAndTitleReady)
    return res.send(videoAndTitleReady);
});

module.exports = router;

Answer 1

此错误是因为您使用的是 res.render。res.render 会尝试渲染页面，因为你必须设置像 jade 等的视图引擎。但在这里你不需要它，所以改变res.render成res.send这样
试试这个

app.use(function(err, req, res, next) {
    // set locals, only providing error in development
    res.locals.message = err.message;
    res.locals.error = req.app.get('env') === 'development' ? err : {};
// render the error page
res.status(err.status || 500);
res.send('error');//this or res.status(err.status || 500).send('error')
});

对于您的第二个问题，您必须像这样在 server.js 中将 bodyParser 放在顶部

app.use(bodyParser.json()); //here
app.use('/', api);

app.use(logger('dev'));

//app.use(bodyParser.json()); your old code

Answer 2

我有同样的错误。我忘记将以下语法添加到 server.js 文件中

//set default engine, and provide [handlebars as] extension
app.set('view engine', 'handlebars');