AJAX Request

Question 1

What is used to exchange data with a server?

Answer 1

XMLHttpRequest

Question 2

How do you send a request to a server?

Answer 2

Use the open() and send() methods of the XMLHttpRequest object.

eg. )
xhttp. open(“GET”, “ajax_info.txt”, true);
xhttp. send();

Question 3

In open(method, url, async), what is the method?

Answer 3

The type of request: GET or POST

Question 4

In open(method, url, async), what is url?

Answer 4

The server (file) location

Question 5

In open(method, url, async), what is async?

Answer 5

Either true(asynchronous) or false (synchronous)

Question 6

The send() method sends the request to the server use for ______.

Answer 6

GET

Question 7

The send(string) method sends the request to the server used for _____.

Answer 7

POST

Question 8

Which is simpler and faster? GET or POST?

Answer 8

GET

Question 9

When should you use POST?

Answer 9

1. A cached file is not an option(update a file or database on the server)
2. Sending a large amount of data to the server (POST has no size limitations).
3. Sending user input (which can contain unknown characters), POST is more robust and secure than GET.

Question 10

Should you use GET or POST when sending large amount of data to the server? and why?

Answer 10

POST because it has no size limits

Question 11

Should you use GET or POST when sending user input. and why?

Answer 11

POST because it is more robust and secure than GET.

Question 12

What is the syntax for a simple GET request?

Answer 12

xhttp. open(“GET”, url, async);

xhttp. send();

Question 13

If you get a cached result in your GET request, what should you do?

Answer 13

Add a unique ID to the URL.

Question 14

What is the syntax for a simple POST request?

Answer 14

xhttp. open(“POST”, url, async);

xhttp. send();

Question 15

What is the ‘setRequestHeader(header, value)

Answer 15

Adds HTTP headers to the request

header: specifies the header name
value: specifies the header value

Question 16

Server requests should be sent _________. and why?

Answer 16

Asynchronously because the JavaScript does not have to wait for the server response.

Question 17

By sending a server request asynchronously, the JavaScript can do what?

Answer 17

1. Execute other scripts while waiting for server response.

2. Deal with the response after the response is ready.

Question 18

With the _______ object you can define a function to be executed when the request receives an answer. The function is defined in the __________ property

Answer 18

XMLHttpRequest, onreadystatechange

Question 19

Why shouldn’t you use a Synchronous XMLHttpRequest? eg.) async = false.

Answer 19

JavaScript will stop executing until the server response is ready. If the server is busy or slow, the application will stop.