Error: response.write is not a function

const router = require("./router.js");

// problem: We need a simple way to look at a user's bagde count and JavaScript point from a web browser

//solution: Use Node.js to perform the profile look ups and server our template via HTTP

//Create a web server
const http = require('http');
const hostname = '127.0.0.1';
const port = 3000;

http.createServer((request, response) => {
  router.home(request,response);
  router.user(request,response);
}).listen(port, hostname);
console.log(`Server running at http://${hostname}:${port}/`);

const Profile = require("./profile.js");
const renderer = require('./renderer.js');

//2. Handle HTTP route GET / and POST/ i.e. Home
function home(request,response) {
  //if the URL == "/" && GET
  if(request.url === "/"){
    response.writeHead(200,{'Content-Type': 'text/plain'});
    renderer.view('header',{},'response');
    response.write("Search\n");
    response.end("Footer\n");
  }
  //if the URL == "/" && POST
    //redirect to / :username
}
//3. Handle HTTP route GET / :username i.e. / fjordani
function user(request,response) {
  if(username.length > 0){
    //show search field
    response.writeHead(200,{'Content-Type': 'text/plain'});
    response.write("Header\n");
    response.write("Search\n");
    response.end("Footer\n");
    //get JSON from threehouse
    const studentProfile = new Profile(username);
    //on end
    studentProfile.on("end", (profileJSON) => {
      //show profile

      //store the needed values
      const values = {
        avatarUrl: profileJSON.gravatar_url,
        username: profileJSON.profile_name,
        badges: profileJSON.badges.length,
        javascriptPoints: profileJSON.points.JavaScript
      }
      //simple response
      response.write(`${values.username} has ${values.badges} badges\n`);
      response.end("Footer\n");
    });
    //on error
    studentProfile.on("error", (error) => {
      //show error
      response.write(error.message+"\n");
      response.end("Footer\n");
    });
  }

}

      // on "error"
        // show error

module.exports.home = home;
module.exports.user = user;

const fs = require('fs');

function view(templateName,values,response) {
  //read from the template file
  const fileContents = fs.readFileSync('./views/' + templateName + '.html');
  //Insert values into the Content

  //write out to the response
  response.write(fileContents);
}

module.exports.view = view;