How to use postm ethod in express code example

Example: 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);
    });

});