Example of callback function example in nodejs

var express = require('express');
var router = express.Router();
var callbackexp={};


router.get('/',function(req,res)

{



console.log("data1");
var example=function (data1)
{
console.log("2");
var data="example";

var ingo=data+data1;
//return ingo;
res.send(ingo);
//console.log(ingo);
}

var infodata=function (callback)
{
console.log("1");
var data="pawank umar";
callback(data);

}
infodata(example);
console.log("3");
res.send("op");
//res.send("hello"+data);




});



module.exports=router;