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Valeri Tandilashvili's Personal Professional Blog
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HTTP Status Codes (TOP 10) 
200 OK
- Standard response for successful HTTP requests 
201 Created
- The request has been fulfilled, resulting in the creation of a new resource 
204 No Content
- The server successfully processed the request and is not returning any content 
304 Not Modified
- Indicates that the resource has not been modified since the version specified by the request headers If-Modified-Since or If-None-Match 
400 Bad Request
- The server cannot or will not process the request due to an apparent client error (e.g., malformed request syntax, too large size, invalid request message framing, or deceptive request routing) 
401 Unauthorized
- Similar to 403 Forbidden, but specifically for use when authentication is required and has failed or has not yet been provided. The response must include a WWW-Authenticate header field containing a challenge applicable to the requested resource 
403 Forbidden
- The request was a valid request, but the server is refusing to respond to it. The user might be logged in but does not have the necessary permissions for the resource 
404 Not Found
- The requested resource could not be found but may be available in the future. Subsequent requests by the client are permissible 
409 Conflict
- Indicates that the request could not be processed because of conflict in the request, such as an edit conflict between multiple simultaneous updates 
500 Internal Server Error
- A generic error message, given when an unexpected condition was encountered and no more specific message is suitable
two ways to include conditional CSS for responsive design
1. include .css file with media attribute:
<link rel="stylesheet" href="responsive.css" media="screen and (max-width: 900px)">
2. @media query without 
<link>
@media screen and (max-width: 900px) {
    /* conditional CSS */
}
checkboxes with the same name 
<input type="checkbox" id="vehicle1" name="vehicle[]" value="Bike">
<label for="vehicle1"> I have a bike</label><br>
<input type="checkbox" id="vehicle2" name="vehicle[]" value="Car">
<label for="vehicle2"> I have a car</label><br>
We can have checkboxes with the same name by putting square brackets at the end of the 
name
value. On server side we receive them whichever is checked as an array
XML tree structure CODE
XML documents form a tree structure that starts at 
the root
An 
XML tree
starts at a 
root element
and branches from the root to 
child elements
<root>
  <child>
    <subchild>.....</subchild>
  </child>
</root>
The terms 
parent
, 
child
, and 
sibling
are used to describe the relationships between elements. ... 
Parents
have children. 
Children
have parents. 
Siblings
are children on the same level (brothers and sisters). ... We can use any of the online XML tree viewer tools to see the document's tree structure, like this one:
https://www.xmlviewer.org/
Books
XML document to see on tree-viewer
<books>
  <book category="cooking">
    <title lang="en">The goals</title>
    <author>Giada De Laurentiis</author>
    <year>2007</year>
    <price>30.00</price>
  </book>
  <book category="children">
    <title lang="en">12 rules for life</title>
    <author>J K. Rowling</author>
    <year>2002</year>
    <price>29.99</price>
  </book>
  <book category="web">
    <title lang="en">The richest man in Babilon</title>
    <author>Erik T. Ray</author>
    <year>2001</year>
    <price>39.95</price>
  </book>
</books>
JSON format comparison with JavaScript objects
JSON names require double quotes. JavaScript names don't. JSON
{ "name": "John" }
In JavaScript we can have names without quotes:
{ name: "John" }
In JavaScript, keys can be strings, numbers, or identifier names:
{ 12: "John" }
In 
JSON
, values must be one of the following data types:
- a string
- a number
- an object (JSON object)
- an array
- a boolean
- null
In 
JavaScript
, values can be all of the above listed types, plus any other valid JavaScript expression, including:
- a function
- a date
- a symbol
- undefined
In 
JSON
, string values must be written with double quotes:
{ "name":"John" }
In 
JavaScript
, we can write string values with double or single quotes:
{ name: 'John' }
using reviver when parsing a JSON string CODE 
JSON.parse(str)
will not convert date string to date object and we get an error
let str = '{"title":"Conference","date":"2017-11-30T12:00:00.000Z"}';

let meetup = JSON.parse(str);

document.write( meetup.date.getDate() ); // Error!
The value of 
meetup.date
is a string, not a 
Date
object. That is why 
JSON.parse
was unable to transform that string into a 
Date
object. ... Passing the reviving function to 
JSON.parse
as the second argument fixes the issue. The reviving function returns all values “as is”, but 
date
will become a 
Date
object and the error will not occur 
let str = '{"title":"Conference","date":"2017-11-30T12:00:00.000Z"}';

let meetup = JSON.parse(str, function(key, value) {
  if (key == 'date') return new Date(value);
  return value;
});

alert( meetup.date.getDate() ); // now works!
HTML5 Content Models 
Metadata
: Content that sets up the presentation or behavior of the rest of the content. These elements are found in the head of the document. Elements: 
<base>
, 
<link>
, 
<meta>
, 
<noscript>
, 
<script>
, 
<style>
, 
<title>
Embedded
: Content that imports other resources into the document. Elements: 
<audio>
, 
<video>
, 
<canvas>
, 
<iframe>
, 
<img>
, 
<math>
, 
<object>
, 
<svg>
Interactive
Content specifically intended for user interaction. Elements: 
<a>
, 
<audio>
, 
<video>
, 
<button>
, 
<details>
, 
<embed>
, 
<iframe>
, 
<img>
, 
<input>
, 
<label>
, 
<object>
, 
<select>
, 
<textarea>
Heading
Defines a section header. Elements: 
<h1>
, 
<h2>
, 
<h3>
, 
<h4>
, 
<h5>
, 
<h6>
, 
<hgroup>
Phrasing
This model has a number of inline level elements in common with HTML4. Elements: 
<img>
, 
<span>
, 
<strong>
, 
<label>
, 
<br />
, 
<small>
, 
<sub>
, ...
resource route
Creates all 7 routes for the resource to cover CRUD functionality
Route::resource('posts', 'PostsController');
These routes are: 
GET
at 
posts
to list all the posts 
POST
at 
posts
to store new post 
GET
at 
posts/create
to show form for creating new post 
GET
at 
posts/{post}
to show the post 
PUT
at 
posts/{post}
to update the post 
DELETE
at 
posts/{post}
to delete the post 
GET
at 
posts/{post}/edit
to show edit form
multiple background images to a single element 
.container {
    background: url(../images/tile.png) left bottom repeat-x,  #FFF url(../images/tile.png) left top repeat-x;
}
XML Attributes 
XML Attribute
specifies a single property for the element, using a 
name/value
pair. An XML-element can have 
one or more
attributes
<a href = "http://www.applications.ge/">Applications.ge</a>
In the example 
href
is the 
attribute name
and 
http://www.applications.ge
is the 
attribute value
... XML attribute names (unlike HTML) are case sensitive. Which means that 
HREF
and 
href
are considered two different XML attributes
<?xml version="1.0"?>
<student>
    <a href="http://www.applications.ge/" hreF="HTTP://applications.ge/">Applications.ge</a>
</student>
Several different values for the same attribute is not allowed. An attribute name must not appear more than once in the same tags:
<?xml version="1.0"?>
<student>
    <a href="http://www.applications.ge/" href="HTTP://applications.ge/">Applications.ge</a>
</student>
The following error will appear on the browser
error on line 3 at column 73: Attribute 
href
 redefined
Attribute names must always be defined without quotation marks, whereas attribute values must always appear in single or double quotation marks
<?xml version="1.0"?>
<student>
    <a "href"="http://www.applications.ge/">Applications.ge</a>
</student>
The following error will appear:
error on line 3 at column 8: error parsing 
attribute name
Attribute values must always be in quotation marks (single 
'
or double 
"
quotes)
<?xml version="1.0"?>
<student>
    <a href=http://www.applications.ge/>Applications.ge</a>
</student>
This incorrect syntax will generate the following error:
error on line 3 at column 13: AttValue: " or ' expected
Results: 1024