app.js

let createError = require('http-errors');
let express = require('express');
let path = require('path');
let cookieParser = require('cookie-parser');
let logger = require('morgan');

let indexRouter = require('./routes/index');
let usersRouter = require('./routes/users');

let app = express();

// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'ejs');

app.use(logger('dev'));
app.use(express.json());
app.use(express.urlencoded({extended: false}));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));

app.all('*', function (req, res, next) {
    {
        res.header("Access-Control-Allow-Origin", "*"); //*表示允许的域名地址，本地则为'则为'http://localhost'
        res.header("Access-Control-Allow-Methods", "PUT,POST,GET,DELETE,OPTIONS");
        res.header("Access-Control-Allow-Headers", "Content-Type, Content-Length, Authorization, X-Powered-By, Accept,X-Requested-With");
        res.header("X-Powered-By", ' 3.2.1');
        res.header("Content-Type", "application/json;charset=utf-8");
        next();
    }
});

app.use('/', indexRouter);
app.use('/users', usersRouter);

// 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');
});

module.exports = app;