Update how-to-access-query-string-parameters.md (#2148)

In accordance with issue #1977, I have updated the Article how-to-access-query-string-parameters with the following changes:

1. Added a note on how to execute the program.
2. Added some detail about other key values provided by `url.parse()`.
3. Some other miscellaneous updates and refactors.

locale/en/knowledge/HTTP/clients/how-to-access-query-string-parameters.md

@@ -9,18 +9,45 @@ layout: knowledge-post.hbs
 
 In Node.js, functionality to aid in the accessing of URL query string parameters is built into the standard library. The built-in `url.parse` method takes care of most of the heavy lifting for us.  Here is an example script using this handy function and an explanation on how it works:
 
-    var fs = require('fs');
-    var http = require('http');
-    var url = require('url') ;
+```js
+const http = require('http');
+const url = require('url');
 
-    http.createServer(function (req, res) {
-      var queryObject = url.parse(req.url,true).query;
-      console.log(queryObject);
+http.createServer(function (req, res) {
+  const queryObject = url.parse(req.url,true).query;
+  console.log(queryObject);
 
-      res.writeHead(200);
-      res.end('Feel free to add query parameters to the end of the url');
-    }).listen(8080);
+  res.writeHead(200, {'Content-Type': 'text/html'});
+  res.end('Feel free to add query parameters to the end of the url');
+}).listen(8080);
+```
 
-The key part of this whole script is this line: `var queryObject = url.parse(req.url,true).query;`. Let's take a look at things from the inside-out.  First off, `req.url` will look like `/app.js?foo=bad&baz=foo`. This is the part that is in the URL bar of the browser. Next, it gets passed to `url.parse` which parses out the various elements of the URL (NOTE: the second paramater is a boolean stating whether the method should parse the query string, so we set it to true). Finally, we access the `.query` property, which returns us a nice, friendly JavaScript object with our query string data. 
+> To test this code run `node app.js` (app.js is name of the file) on the terminal and then go to your browser and type `http://localhost:8080/app.js?foo=bad&baz=foo` on the URL bar
 
+The key part of this whole script is this line: `const queryObject = url.parse(req.url,true).query;`. Let's take a look at things from the inside-out.  First off, `req.url` will look like `/app.js?foo=bad&baz=foo`. This is the part that is in the URL bar of the browser. Next, it gets passed to `url.parse` which parses out the various elements of the URL (NOTE: the second paramater is a boolean stating whether the method should parse the query string, so we set it to true). Finally, we access the `.query` property, which returns us a nice, friendly JavaScript object with our query string data. 
 
+The `url.parse()` method returns an object which have many key value pairs one of which is the `query` object. Some other handy information returned by the method include `host`, `pathname`, `search` keys.
+
+In the above code:
+- `url.parse(req.url,true).query` returns `{ foo: 'bad', baz: 'foo' }`.
+- `url.parse(req.url,true).host` returns `'localhost:8080'`.
+- `url.parse(req.url,true).pathname` returns `'/app.js'`.
+- `url.parse(req.url,true).search` returns `'?foo=bad&baz=foo'`.
+
+### Parsing with querystring
+
+Another way to access query string parameters is parsing them using the `querystring` builtin Node module.
+
+This method, however, must be passed just a querystring portion of a url. Passing it the whole url, like you did in the `url.parse` example, won't parse the querystrings.
+
+```js
+const querystring = require('querystring');
+const url = "http://example.com/index.html?code=string&key=12&id=false";
+const qs = "code=string&key=12&id=false";
+
+console.log(querystring.parse(qs));
+// > { code: 'string', key: '12', id: 'false' }
+
+console.log(querystring.parse(url));
+// > { 'http://example.com/index.html?code': 'string', key: '12', id: 'false' }
+```