A simple json file based database server

dbservertofile.js

var http = require('http');
var url = require('url');
var fs = require('fs');
var DB_FILE = 'database.json';

function init(){
	//create file if it's present.
	//synchronous because it needs to happen before requests can be processed
	if(!fs.existsSync(DB_FILE)){
		console.log(`Initialising storage.\n -Creating ${DB_FILE} file`);
		fs.writeFileSync(DB_FILE,"{}");
	}
}

function readFromFile(callback){
		fs.readFile(DB_FILE,'utf-8',callback);
}

function writeToFile(data,callback) {
		fs.writeFile(DB_FILE,data,callback);
}

function getData(callback){
	readFromFile(callback);
}

function setData(data,callback) {
	//parse object to json string
	var dataString = JSON.stringify(data);
	writeToFile(dataString,callback)
}

http.createServer(function(req, res){
	//use querystring module on query strings and stores in 'query' object
	var parseUrl = url.parse(req.url, true, true);
	var statusCode = 404;
	var content = "404 - Not Found"

	//simple routing
	if(parseUrl.pathname === "/set"){
		console.log("Inserting value into database:",parseUrl.query);
		statusCode = 200;

		//retrieve current state of file (async)
		getData(function(err,dataString){

			if(err)
				throw err;


			//parse json string
			var data = JSON.parse(dataString);



			//assign new query object's contents. don't forget previous state of 'data'
			Object.assign(data,parseUrl.query,data);

			//persist data in file (async)
			setData(data, function(err){
				if(err)
					throw err;

				content = "Data inserted";
				res.writeHead(statusCode,{"Content-Type":"text/plain"});
				res.end(content);
			});

		});

	}else if(parseUrl.pathname === "/get"){
		var searchKey = parseUrl.query.key;
		console.log("Retrieving value from database: key="+searchKey);
		statusCode = 200;

		//get search key
		getData(function(err, dataString){

			var data = JSON.parse(dataString);


			content = data[searchKey];

			res.writeHead(statusCode,{"Content-Type":"text/plain"});
			res.end(content);
		});

	}else{
			res.writeHead(statusCode,{"Content-Type":"text/plain"});
			res.end(content);
	}

}).listen(4000);

//file initialiser
init();
console.log("Started DB server...");