How do we use XMLHttpRequest object in JavaScript?

Below is a code snippet which shows how to use XMLHttpRequest object. In this code snippet we are sending a GET request on the local IIS. Below is the explanation of the code snippet according to the numbers specified in the code snippet.
1,2,3,4 - This is like checking which is this browser and create the objects accordingly. XMLHttpRequest objects have different ways of technical implementation according to different browsers. In Internet explorer it’s an activex object but in other browsers its XMLHttpRequest. So if windows.XMLHttpRequest does not return null then we can create XMLHttpRequest object. If it returns null then we can try creating the activex object Microsoft.XMLHttp object. In case it fails probably then probably we have an older version of XML that is MSXML2. So in the error handling we will try to create the MSXML2 object.
5:- In this snippet we OPEN the connection to the local host server and specify what type of request we are using. In this case we are using the GET method.
6:- Finally we make a request to the server.
7:- Here we get the request sent by the server back to the client browser. This is a blocking call as we need to wait to get the request back from the server. This call is synchronous that means we need to wait for the response from the server.