add an explaination about XHR

AbdulRahmanDbes · AbdulRahmanDbes · commit 0d9950381bcb · 2017-10-21T15:27:22.000+02:00
diff --git a/Week5/REVIEW.MD b/Week5/REVIEW.MD
@@ -13,51 +13,51 @@ this review covers:
 
 - JavaScript callback functions tutorial: https://www.youtube.com/watch?v=pTbSfCT42_M&index=17&list=WL
 
-## XMLHTtpRequest
-**XMLHttpRequest** is an objects to interact with servers. You can retrieve data from a URL without having to do a full page refresh. XMLHttpRequest is used heavily in Ajax programming. - [MDN](https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest)
+## XMLHttpRequest
+**XMLHttpRequest** is an objects to interact with servers. You can retrieve data from a URL without having to do a full page refresh. XMLHttpRequest is used heavily in Ajax programming - [MDN](https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest).
 
 So what is Ajax?
 **Ajax** is a method of exchanging data with a server, and updating parts of a web page without reloading the entire page.
 
-Let's diving a bit deeply into the code:
+Let's diving into the code:
 
-First, we need to make an instance from 'XMLHttpRequest' class.
+First, we need to make an instance from 'XMLHttpRequest' object.
 ```javascript
 var http = new XMLHttpRequest();
 ```
 When we are doing a request it goes through 5 states:
-* 0 : request not initialized.
+* 0 : request is not initialized.
 * 1 : request has been set up.
 * 2 : request has been sent.
 * 3 : request is in process.
 * 4 : request is complete.
 
-In the code below we are checking if the request is complete or not, and we check the status == 200 just to make sure that we do not get 404 error. - Take a look about [HTTP Status Code](https://httpstatuses.com).
+In the code below we are checking if the request is complete or not, and we check the status == 200 just to make sure that we do not get 404 error - Take a look about [HTTP Status Code](https://httpstatuses.com).
 ```javascript
  http.onreadystatechange = function() {
         if ( http.readyState == 4 && http.status == 200) {
-             console.log(`Response from the server: ${http.response}`); 
+             console.log('Response from the server: ' + http.response); 
      }
 }
 ```
 There are methods to deal with a server like (GET, POST, UPDATE, DELETE…)
 
-* GET: to retrieve data from server.
-* POST: to send data to server.
-* UPDATE: to update data on the server.
-* DELETE: to delete date from the server.
+* GET: retrieve data from server.
+* POST: send data to server.
+* UPDATE: update data on the server.
+* DELETE: delete date from the server.
 
-To Initialize a request we use [open][https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/open] method. The syntax is:
+To initialize a request we use [open](https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/open) method. The syntax is:
 ```javascript
-XMLHttpRequest.open(method, url, async, user, password)
+XMLHttpRequest.open(method, url, async, user, password);
 ```
-The parameters 'method' and 'url' are mandatory, 'user' and 'password' are optional. True is a default value for 'async'.
+The parameters _method_ and _url_ are mandatory, _user_ and _password_ are optional. True is a default value for _async_.
 
 ```javascript
 http.open("GET", URL, true/false);
 ```
-At the end we have to send our request to the server through [send](https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/send) method. In our situation we are retriving a data from the server, so we do not have to pass any parameter to the send request.
+At the end we have to send our request to the server through [send](https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/send) method. In our situation we are retrieving a data from the server, so we do not have to pass a parameter to the send request.
 
 ```javascript
-http.send()
+http.send();
 ```
