app.js

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

var usuario = require('./routes/usuario');
var libro = require('./routes/libro');
var prestamo = require('./routes/prestamo');

var app = express();
//////
// Activar el CORS
app.use(function (req, res, next) {
  res.header("Access-Control-Allow-Origin", "*");
  res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
  next();
});

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

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')));

try{

app.use('/usuario', usuario);
app.use('/libro', libro);
app.use('/prestamo', prestamo);

} catch(e){
  
}

// 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;