AJAX

Question 1

What does AJAX stand for?

Answer 1

Asynchronous
Javascript
And
XML

Question 2

What is AJAX used for?

Answer 2

Using Javascript on server after webpage has loaded to get more information in the form of XML (or JSON)

Question 3

What is XML used for?

Answer 3

Store data
Transfer data
Terminology
it's a data format that sits there
contract

Question 4

What problems exist with cross domain policies in browsers? What’s a solution?

Answer 4

You are not allowed to make AJAX requests to a webpage perceived to be on a different server by the browser
JSONP is a solution

Question 5

What does JSON stand for?

Answer 5

JavaScript
Object
Notation

Question 6

What is the advantage to using JSON over XML?

Answer 6

JSON files look same as code used to create JS objects
eval() function in JS converts JSON to JS objects (eval used when using JSON instead of JSONP)
make sure you trust where you are getting this code from

Question 7

What are some features of JSON?

Answer 7

Data is in name/value pairs
Data is separated by commas
Curly braces hold objects
Square brackets hold arrays

Question 8

When would we use JSON over XML

Answer 8

• Messages don’t need to be validated, or validating their deserialization is simple
• You’re not transforming messages, or transforming their deserialization is simple
• Your messages are mostly data, not marked-up text
• The messaging endpoints have good JSON tools

Question 9

Why would we want processing to happen at client end rather than our server?

Answer 9

It costs us less

Question 10

What does asynchronous mean? What about synchronous?

Answer 10

Asynchronous means that the browser will make the AJAX request and continue doing other things. Synchronous means the browser will stop what it’s doing until the AJAX call completes (has limited use case – sneaker drops).

Question 11

When would we use XML over JSON?

Answer 11

• You need message validation
• You’re using XSLT
• Your messages include a lot of marked-up text
• You need to interoperate with environments that don’t support JSON

Question 12

Explain the process of an AJAX call being sent out

Answer 12

1) Browser: Event occurs so XMLHttpRequest object created and HttpRequest sent to internet
2) Servers: Process request, send response and data through internet back to browser
3) Browser: Process data using JS and update content

Question 13

Explain how AJAX violates security rules regarding percent escaping of reserved characters in POST data

Answer 13

Allows direct injection of hostile code into SQL schemas, which can be things such as PHP code for later retrieval and execution on the host.

Question 14

Why can’t AJAX be trusted to do complete scanning over every communication?

Answer 14

It doesn’t escape reserved GET and POST characters. Allows direct injection of hostile code into SQL schemas.