database server, for the hacker school interview.

index.js

// require the http module
var http = require('http');

// require the util module to format things
var util = require('util');

//the get regex matches /get and whatever and the set regex matches /set and whatever
var getRegex = /\/get.*/, setRegex = /\/set.*/, database = {};

// create a server with the 'handler' function and start listening on 4000
http.createServer(handler).listen(4000);

function handler(req, res) {
        // get the url and extract the params
        var url = req.url, urlParams = extract(url);
        // if there are any,
        if(urlParams) {
                // test to see if the url matches a set command
                if(setRegex.test(url)) {
                        //if it does, update the database and let the user know what he did
                        database[urlParams.key] = urlParams.value;
                        res.end(util.format('you set \'%s\' to value %s', urlParams.key, urlParams.value));
                }
                // test to see if it's a get command
                if(getRegex.test(url)) {
                        // if it is, make sure the user is issuing the 'key' param, and get whatever's in the database.
                        urlParams.key === 'key' && res.end(database[urlParams.value]);
                }
        }
        // if no route matches (or no criteria matches) get a friendly message to him.
        res.end(util.format('Hello! This is database server.\nUse /set?somekey=somevalue to map \'key\' to \'value\'\nand /get?key=somekey to get what\'s under the key \'key\'.'));
}

// the extract function receives a url and breaks it up to find the query string.
function extract(url) {
        // first, extract what's after the '?' sign.
        // at the left, there is a route. at the right, what's after it
        // get the right and split it on '=', left is key, right is value.
        // if nothing is there, defaults to null.
        var params = url.indexOf('?') >= 0 ? url.split('?')[1].split('=') : null;

        // if there is something, return an object with the key and value as 'key' and 'value'.
        return params && { key: params[0], value: params[1] };
}