AJAX/ES6

Question 1

What is a client?

Answer 1

A computer or program that request services from a server

Question 2

What is a server?

Answer 2

A computer or program (or process) that runs the service to be shared with clients

Question 3

Which HTTP method does a browser issue to a web server when you visit a URL?

Answer 3

GET

Question 4

What three things are on the start-line of an HTTPrequestmessage?

Answer 4

1. An HTTP method (GET, PUT, POST)
2. The request target (usually a URL, everything after the domain, aka after the http://example.com/, Aks the query string)
3. The HTTP version, the expected version to use for the response

Question 5

What three things are on the start-line of an HTTPresponsemessage?

Answer 5

1. The Protocol version (usually HTTP.1.1)
2. The status code, indicating success or failure of the request (200 OK, 200s are successful, 404, 302 common)
3. A status text, brief description of the status code

Question 6

What are HTTP headers?

Answer 6

Additional information shared between client and servers in a response (like location or the server providing it) or request (like information of the client requesting the resource)

For example,a request message can use headers to indicate it’s preferred media formats, while a response can use header to indicate the media format of the returned body.

Question 7

Where would you go if you wanted to learn more about a specific HTTP Header?

Answer 7

MDN

Question 8

Is a body required for a valid HTTP request or response message?

Answer 8

No, it is not required. It would include data associated with the request (like content of an HTML form)

Question 9

What is AJAX?

Answer 9

A technique used for loading data into a page without having to refresh the entire page

Question 10

What does the AJAX acronym stand for?

Answer 10

Asynchronous JavaScript And XML(Extensible markup language)

Question 11

Which object is built into the browser for making HTTP requests in JavaScript?

Answer 11

XMLHttpRequest object (xhr)

Question 12

What event is fired byXMLHttpRequestobjects when they are finished loading the data from the server?

Answer 12

Load event

Question 13

Bonus Question: AnXMLHttpRequestobject has anaddEventListener()method just like DOM elements. How is it possible that they both share this functionality?

Answer 13

They have a shared prototype object

Question 14

What is a code block? What are some examples of a code block?

Answer 14

Any code within curly braces
If else statements, for statements, do while statements

Question 15

What does block scope mean?

Answer 15

It will not be accessible from outside the block that its in

Question 16

What is the scope of a variable declared withconstorlet?

Answer 16

Block-scope

Question 17

What is the difference betweenletandconst?

Answer 17

Const cannot be reassigned
Const must be initialized during declaration
(Let can be updated but CANNOT be re-declared, const also cannot be re-declared)

Question 18

Why is it possible to.push()a new value into aconstvariable that points to anArray?

Answer 18

Because the you can still change a const variable’s property values

Question 19

How should you decide on which type of declaration to use?

Answer 19

Use let if you know the variable will need to be reassigned

Question 20

What is the syntax for writing a template literal?

Answer 20

Wrapping text with back ticks
Let msg = this text can span multiple lines;

${} for substitutions

Question 21

What is “string interpolation”?

Answer 21

The ability to substitute parts of a string for values of variables or expressions

Question 22

What is destructuring, conceptually?

Answer 22

Syntax shortcut for assigning properties of an object/elements of an array to individual variables.

Question 23

What is the syntax forObjectdestructuring?

Answer 23

let { property1: var1, property2: var 2 } = objectName;

Question 24

What is the syntax forArraydestructuring?

Answer 24

const arr = [1, 2, 3];
const [ var1, var2, var3 ] = arr;

Question 25

How can you tell the difference between destructuring and creatingObject/Arrayliterals?

Answer 25

Creating object/array literal -> object/array literal on right side of assignment operator

Destructuring assignment -> things that looks like an object/array literal on left side of assignment operator

Question 26

What is the syntax for defining an arrow function?

Answer 26

(parameters) => { statements }

Question 27

When an arrow function’s body is left without curly braces, what changes in its functionality?

Answer 27

It will be an expression and you do not need a return keyword