creditDemo/app.js

const express = require('express');
const sdt = require('silly-datetime');
const app = express();
const PORT = 1523;
app.use(express.json());

var balance = 0;

// 消费
app.post("/purchase", (req, res) => {
    const value = parseFloat(req.body.amount);
    if (isNaN(value) || !isFinite(req.body.amount)) {
        res.status(400).send(JSON.stringify({code: -102, message: "Illegal data", data: {balance: balance}}));
        return;
    }
    if(value < 0) {
        res.status(400).send(JSON.stringify({code: -101, message: "Amount must be positive.", data: null}));
    } else {
        if (balance - value < 0) {
            res.status(200).send(JSON.stringify({code: 101, message: "Insufficient balance.", data: null}));
            return;
        }
        balance -= value;
        res.status(200).send(JSON.stringify({code: 0, message: "purchased", data: {balance: balance}}));
    }
});

// 充值
app.post("/recharge", (req, res) => {
    const value = parseFloat(req.body.amount);
    if (isNaN(value) || !isFinite(req.body.amount)) {
        res.status(400).send(JSON.stringify({code: -102, message: "Illegal data", data: null}));
        return;
    }
    balance += value;
    res.status(200).send(JSON.stringify({code: 0, message: "recharged", data: {balance: balance}}));
});

app.get("/balance", (req, res) => {
    res.status(200).send(JSON.stringify({code: 0, message: "success", data: {balance: balance}}))
});

app.listen(PORT, () => console.log(`Listening on port ${PORT}`));