req.params,req.query是用在get请求当中

1、req.params

//例子 http://localhost:3000/1234

app.get("/:id",function (req,res) {

res.send(req.params["id"]);

});

把请求 / 后面的参数当成id，通过req.params就能获取到id，返回页面也就是1234

2、req.query

// http://localhost:3000/?id=10

app.get("/",function (req,res) {
    res.send(req.query["id"]);
});

如果有两个或以上参数，用 & 连接，如：/?id=2&name=node, 获取参数则是：req.query.id 得到 1 , req.query.name 得到 node 

req.body是用在post请求当中

1、body-parser中间件写法（已弃用）

var express = require('express')
var bodyParser = require('body-parser')
const cors = require('cors');
var app = express();
//解决跨域
app.use(cors());
app.use(bodyParser.urlencoded({extended:false}));
app.use(bodyParser.json())
app.post('/service/update', (req, res) => {
  console.log("res",req.body)
})
app.listen(3000, function () {
  console.log('app is runing at port 3000');
})

2、express最新版版内置了post参数解析,可以直接调用express

var express = require('express')
const cors = require('cors');
var app = express();
//解决跨域
app.use(cors());
app.use(express.urlencoded({ extended: false }))
app.use(express.json())
app.post('/service/update', (req, res) => {
  console.log("res",req.body)
})
app.listen(3000, function () {
  console.log('app is runing at port 3000');
})