Server Example

server.js

"use strict";
//Imports
const http = require("http");
const url = require("url");
const queryString = require("querystring");
const StringDecoder = require("string_decoder").StringDecoder;

// ports for the process
const httpPort = 4443;

// http server
const serverHttp = http.createServer((req, res) => {
  serverLogic(req, res);
});
let countNumber = 0;
serverHttp.listen(httpPort, () => {
  console.log("http server started in at port " + httpPort);
});
const handler = {
  count: (data, cb) => {
    const {
      method
    } = data;
    const allowedMethods = ["post", "get"];

    if (allowedMethods.indexOf(method) !== -1) {
      handler._count[method](data, cb);
    } else {
      cb(
        405, {
          err: "unknown method"
        },
        "json"
      );
    }
  },
  _count: {
    post: (data, cb) => {
      const {
        payload: {
          value
        }
      } = data;
      countNumber = value;
      cb(200, {
        sucess: true
      }, "json");
    },
    get: (data, cb) => {
      cb(200, {
        value: countNumber
      }, "json");
    }
  }
};
const handleNotFound = (data, cb) => {
  cb(404, {});
};

const serverLogic = (req, res) => {
  //getting the url from the request and parseing it with url.parser and querystring
  const parserdUrl = url.parse(req.url, true);

  // removing front and end slash from the url
  const trimedUrl = parserdUrl.pathname.replace(/^\/|\/$/g, "");

  //getting headers and method from req
  let {
    headers,
    method
  } = req;

  // turning the method to lowercase
  method = method.toLowerCase();

  // getting query
  let queryParameter = parserdUrl.query;
  // getting the data from the req
  let buffer = "";
  // decoding the buffer to string
  const decoder = new StringDecoder("utf-8");
  req.on("data", function(data) {
    buffer += decoder.write(data);
  });
  req.on("end", function() {
    buffer += decoder.end();
    if (buffer) {
      if (headers["content-type"] === "application/x-www-form-urlencoded")
        buffer = queryString.parse(buffer);
      if (headers["content-type"] === "application/json")
        buffer = JSON.parse(buffer);
    }
    const chooseHandler =
      trimedUrl in handler ? handler[trimedUrl] : handleNotFound;
    const data = {
      payload: buffer,
      queryParameter,
      method,
      headers,
      parserdUrl,
      trimedUrl
    };
    try {
      // selecting a handler
      chooseHandler(data, (statusCode, payload, contentType) => {
        processHandler(res, statusCode, payload, contentType);
      });
    } catch (e) {
      console.log(e);
      whenError(res);
    }
  });
};

const whenError = res => {
  res.writeHead(500);
  res.end("error");
};

const processHandler = (res, statusCode, payload, contentType) => {
  // setting up content type header for response
  if ((contentType = "json")) {
    payload = JSON.stringify(payload);
    res.setHeader("Content-Type", "application/json");
  }
  res.writeHead(statusCode);
  res.end(payload);
};