Concepts

Question 0

AJAX and its purposes

Answer 0

• Asynchronous Javcascript and XML

Purposes

• request information from a web server
• update content on a web page without loading a new web page
• post data to a web server
• able to use AJAX with any server-side language

Question 1

Asynchronous

Answer 1

• callbacks for multiple AJAX requests may not run in the order the requests were sent
• servers may take longer to respond to certain requests, so callbacks run in the order in which the responses return

Question 2

GET

Answer 2

• requests a new web page, CSS file, or image
• “get” information from a web server
• send data in the URL

Question 3

Programming Process

Answer 3

1. Create an XMLHTTP Request object
2. Create a callback function
3. Open a request
4. Send the request
5. var xhr = new XHMLHttpRequest();
6. xhr.onreadystatechange = function() {};
7. xhr.open(‘GET’, ‘data/employees.json’);
8. xhr.send();

Question 4

Query String

Answer 4

• information sent to the web server

- it is added to the end of a URL

Question 5

POST

Answer 5

• used with web forms to send data in a database
• sending data to store, delete, or update information from a database
• send more than 2083 characters of data to the web server
• sends data in the “body” of the request

Question 6

Security Limitations

Answer 6

• same-origin policy

Circumventions

• create a web proxy
• JSON with Padding (JSON)
• Cross-Origin Resource Sharing (CORS)

Question 7

Web Proxy

Answer 7

• it allows you to bypass a web brower’s same origin policy by retrieving data from another server, while keeping AJAX requests within the same domain