how to set up to recieve a post in express code example

Example 1: express get params after ?

GET /something?color1=red&color2=blue

app.get('/something', (req, res) => {
    req.query.color1 === 'red'  // true
    req.query.color2 === 'blue' // true
})

Example 2: app.post (req res) get data

const express=require('express');
const app=express();
//accept Post with no midleWare express
app.post("/register/",function(req,res){
    var bodyStr = '';
    req.on("data",function(chunk){
        bodyStr += chunk.toString();
    });
    req.on("end",function(){
        res.send(bodyStr);
    });

});