error runing nodejs

PS C:\Angular3\mean-course> node server.js
C:\Angular3\mean-course\server.js:47
app.set("port", port);
    ^

TypeError: app.set is not a function
    at Object.<anonymous> (C:\Angular3\mean-course\server.js:47:5)
    at Module._compile (internal/modules/cjs/loader.js:778:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:789:10)
    at Module.load (internal/modules/cjs/loader.js:653:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:593:12)
    at Function.Module._load (internal/modules/cjs/loader.js:585:3)
    at Function.Module.runMain (internal/modules/cjs/loader.js:831:12)
    at startup (internal/bootstrap/node.js:283:19)
    at bootstrapNodeJSCore (internal/bootstrap/node.js:622:3)
PS C:\Angular3\mean-course> npm install
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@1.2.9 (node_modules\webpack-dev-server\node_modules\fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@1.2.9: wanted {"os":"darwin","arch":"any"} (current: {"os":"win32","arch":"x64"})
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@1.2.9 (node_modules\watchpack\node_modules\fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@1.2.9: wanted {"os":"darwin","arch":"any"} (current: {"os":"win32","arch":"x64"})
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@2.1.2 (node_modules\nodemon\node_modules\fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@2.1.2: wanted {"os":"darwin","arch":"any"} (current: {"os":"win32","arch":"x64"})
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@1.2.9 (node_modules\karma\node_modules\fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@1.2.9: wanted {"os":"darwin","arch":"any"} (current: {"os":"win32","arch":"x64"})
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@1.2.9 (node_modules\@angular\compiler-cli\node_modules\fsevents):npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@1.2.9: wanted {"os":"darwin","arch":"any"} (current: {"os":"win32","arch":"x64"})
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@2.0.7 (node_modules\fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@2.0.7: wanted {"os":"darwin","arch":"any"} (current: {"os":"win32","arch":"x64"})

audited 17388 packages in 34.458s
found 16 vulnerabilities (4 moderate, 12 high)
  run `npm audit fix` to fix them, or `npm audit` for details
PS C:\Angular3\mean-course> node server.js
C:\Angular3\mean-course\server.js:47
app.set("port", port);
    ^

TypeError: app.set is not a function
    at Object.<anonymous> (C:\Angular3\mean-course\server.js:47:5)
    at Module._compile (internal/modules/cjs/loader.js:778:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:789:10)
    at Module.load (internal/modules/cjs/loader.js:653:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:593:12)
    at Function.Module._load (internal/modules/cjs/loader.js:585:3)
    at Function.Module.runMain (internal/modules/cjs/loader.js:831:12)
    at startup (internal/bootstrap/node.js:283:19)
    at bootstrapNodeJSCore (internal/bootstrap/node.js:622:3)
PS C:\Angular3\mean-course> npm run start:server

> mean-course@0.0.0 start:server C:\Angular3\mean-course
> nodemon server.js

[nodemon] 2.0.2
[nodemon] to restart at any time, enter `rs`
[nodemon] watching dir(s): *.*
[nodemon] watching extensions: js,mjs,json
[nodemon] starting `node server.js`
C:\Angular3\mean-course\server.js:47
app.set("port", port);
    ^

TypeError: app.set is not a function
    at Object.<anonymous> (C:\Angular3\mean-course\server.js:47:5)
    at Module._compile (internal/modules/cjs/loader.js:778:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:789:10)
    at Module.load (internal/modules/cjs/loader.js:653:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:593:12)
    at Function.Module._load (internal/modules/cjs/loader.js:585:3)
    at Function.Module.runMain (internal/modules/cjs/loader.js:831:12)
    at startup (internal/bootstrap/node.js:283:19)
    at bootstrapNodeJSCore (internal/bootstrap/node.js:622:3)
[nodemon] app crashed - waiting for file changes before starting...

const app = require("./backend/app");
const debug = require("debug")("node-angular");
const http = require("http");

const normalizePort = val => {
  var port = parseInt(val, 10);

  if (isNaN(port)) {
    // named pipe
    return val;
  }

  if (port >= 0) {
    // port number
    return port;
  }

  return false;
};

const onError = error => {
  if (error.syscall !== "listen") {
    throw error;
  }
  const bind = typeof port === "string" ? "pipe " + port : "port " + port;
  switch (error.code) {
    case "EACCES":
      console.error(bind + " requires elevated privileges");
      process.exit(1);
      break;
    case "EADDRINUSE":
      console.error(bind + " is already in use");
      process.exit(1);
      break;
    default:
      throw error;
  }
};

const onListening = () => {
  const addr = server.address();
  const bind = typeof port === "string" ? "pipe " + port : "port " + port;
  debug("Listening on " + bind);
};

const port = normalizePort(process.env.PORT || "3000");
app.set("port", port);

const server = http.createServer(app);
server.on("error", onError);
server.on("listening", onListening);
server.listen(port);


script
const express = require('express');

const app = express();

app.use((req,res,next) =>{
    console.log('First Middleware');
    next();
});


app.use((req,res,next) =>{
    res.send('hello form express');
});

module.export = app;