我是express.js的新手，在我的一个路由中使用PUT请求更新customers数组（用作“数据库”）中的一个客户时遇到问题。请参见下面我的app.js：

const express = require('express');

const app = express();
const PORT = process.env.PORT || 3000;

app.use(express.json());

// Body parser
const bodyParser = require('body-parser');
app.use(bodyParser.json());

// cors middleware
const cors = require('cors');
app.use(cors());

//const apiRouter = require('./routes/api');
//app.use('/api', apiRouter);

// get all customers
app.get('/api/customers', (req, res) => {
    res.send(customers);
})
const customers = [
    {
        name: 'John',
        id: 1,
        age: 30
    },
    {
        name: 'Mark',
        id: 2,
        age: 10
    },
    {
        name: 'Andrew',
        id: 3,
        age: 60
    }
]

/// get a customer by id 
app.get('/api/customers/:id', (req, res) => {
    const found = customers.some(customer => customer.id === parseInt(req.params.id));

    if (found) {
        res.json(customers.filter(customer => customer.id === parseInt(req.params.id)))
    } else {
        res.status(400).json({ msg: `No customers found with id ${req.params.id}` })
    }
})

// update a  customer 
// look up the customer, if not found return 404, else update the customer and return the updated customer
app.put('/api/customers/:id', (req, res) => {

    const customer = customers.find(c => c.id === parseInt(req.params.id));
    if (!customer) {
        res.status(404).res.send(`The customer with id ${req.params.id} was not found`);
    } else {
        customer.name = req.body.name;
        customer.age = req.body.age;
        res.send(customer);
    }

})

app.listen(PORT, (error) => {
    if (!error) {
        console.log("Server is Successfully Running and App is listening on port" + PORT)
    }
    else {
        console.log("Error occurred, server can't start", error);
    }
});

module.exports = app;

我正在使用 Postman ，并试图检索更新的客户之间的现有的，但它只创建一个新的一个与他的ID，但姓名和年龄没有显示，即使在“身体”选项指定的 Postman 。我知道这可能是愚蠢的，但卡住了一段时间。任何帮助将不胜感激。