onLoad() {
            uni.request({
                //localhost也可以换成本地局域网ip地址,192.168.xxxx
                url: 'http://localhost:3000/getlist',
                success: (res) => {
                    // console.log(res);
                    // console.log(res.data);
                    this.xxdata = res.data
                }
            })
        },

全局安装 express和express-generator
在某处文件夹，打开命令窗口，输入express myxxx
此时会自动创建很多文件，
cd myxxx
npm install
npm start
在浏览器输入http://localhost:3000，后端服务就启动了

继续安装nodedemo，下载成功后，在package.json中新增一行    "start1": "nodemon ./bin/www"
目的是为了修改代码的时候，不用反复重启了，运行也变成了npm start1

自行配置了sql，创建db文件夹，在内部创建sql.js
const mysql = require('mysql');
const connection = mysql.createConnection({
    host: 'localhost',
    user: 'root',
    password: 'root',
    port: 3307,
    database: 'demo1'

})
module.exports = connection

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改造routes中的index.js，使得数据是数据库获取的
var express = require('express');
var router = express.Router();
var connction = require('../db/sql.js')

// 解决跨域问题
router.all("*", function (req, res, next) {
  res.header("Access-Control-Allow-Origin", "*");
  res.header("Access-Control-Allow-Headers", "X-Requested-With");
  res.header("Access-Control-Allow-Methods", "PUT,POST,GET,DELETE,OP0TIONS");
  res.header("X-Powered-By", "Express");
  res.header("Content-Type", "text/html; charset=UTF-8");
  next();
});

/* GET home page. */
router.get('/', function (req, res, next) {
  res.render('index', {
    title: 'Express1xx'
  });
});



router.get('/list', function (req, res, next) {
  res.send({
    "code": 1,
    data: [{
      id: 1,
      name: 'html'
    },
    {
      id: 2,
      name: 'css'
    },
    {
      id: 3,
      name: 'javascript'
    },
    ]
  })
});



router.get('/getlist', function (req, res, next) {
  connction.query('select * from users', function (error, results, fields) {
    if (error) {
      result = {
        warn: 'err',
        message: '获取数据库时发生搓搓'
      }
      res.send(result)
    } else {
      res.send(results)
    }
  })
});

module.exports = router;