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Thursday, February 23, 2017

HTML5 - Quick Guide

HTML5 - Overview

HTML5 is the next major revision of the HTML standard superseding HTML 4.01, XHTML 1.0, and XHTML 1.1. HTML5 is a standard for structuring and presenting content on the World Wide Web.
HTML5 is a cooperation between the World Wide Web Consortium (W3C) and the Web Hypertext Application Technology Working Group (WHATWG).

The new standard incorporates features like video playback and drag-and-drop that have been previously dependent on third-party browser plug-ins such as Adobe Flash, Microsoft Silverlight, and Google Gears.

Browser Support

The latest versions of Apple Safari, Google Chrome, Mozilla Firefox, and Opera all support many HTML5 features and Internet Explorer 9.0 will also have support for some HTML5 functionality.
The mobile web browsers that come pre-installed on iPhones, iPads, and Android phones all have excellent support for HTML5.

New Features

HTML5 introduces a number of new elements and attributes that helps in building a modern website. Following are great features introduced in HTML5.
  • New Semantic Elements − These are like <header>, <footer>, and <section>.
  • Forms 2.0 − Improvements to HTML web forms where new attributes have been introduced for <input> tag.
  • Persistent Local Storage − To achieve without resorting to third-party plugins.
  • WebSocket − A a next-generation bidirectional communication technology for web applications.
  • Server-Sent Events − HTML5 introduces events which flow from web server to the web browsers and they are called Server-Sent Events (SSE).
  • Canvas − This supports a two-dimensional drawing surface that you can program with JavaScript.
  • Audio & Video − You can embed audio or video on your web pages without resorting to third-party plugins.
  • Geolocation − Now visitors can choose to share their physical location with your web application.
  • Microdata − This lets you create your own vocabularies beyond HTML5 and extend your web pages with custom semantics.
  • Drag and drop − Drag and drop the items from one location to another location on a the same webpage.

Backward Compatibility

HTML5 is designed, as much as possible, to be backward compatible with existing web browsers. New features build on existing features and allow you to provide fallback content for older browsers.
It is suggested to detect support for individual HTML5 features using a few lines of JavaScript.
If you are not familiar with any previous version of HTML, I would recommend to go through our HTML Tutorial before you explore further concepts of HTM5.

HTML5 - Syntax

The HTML 5 language has a "custom" HTML syntax that is compatible with HTML 4 and XHTML1 documents published on the Web, but is not compatible with the more esoteric SGML features of HTML 4.
HTML 5 does not have the same syntax rules as XHTML where we needed lower case tag names, quoting our attributes,an attribute had to have a value and to close all empty elements.
But HTML5 is coming with lots of flexibility and would support the followings −
  • Uppercase tag names.
  • Quotes are optional for attributes.
  • Attribute values are optional.
  • Closing empty elements are optional.

The DOCTYPE

DOCTYPEs in older versions of HTML were longer because the HTML language was SGML based and therefore required a reference to a DTD.
HTML 5 authors would use simple syntax to specify DOCTYPE as follows −
<!DOCTYPE html>
All the above syntax is case-insensitive.

Character Encoding

HTML 5 authors can use simple syntax to specify Character Encoding as follows −
<meta charset="UTF-8">
All the above syntax is case-insensitive.

The <script> tag

It's common practice to add a type attribute with a value of "text/javascript" to script elements as follows −
<script type="text/javascript" src="scriptfile.js"></script>
HTML 5 removes extra information required and you can use simply following syntax −
<script src="scriptfile.js"></script>

The <link> tag

So far you were writing <link> as follows −
<link rel="stylesheet" type="text/css" href="stylefile.css">
HTML 5 removes extra information required and you can use simply following syntax −
<link rel="stylesheet" href="stylefile.css">

HTML5 Elements

HTML5 elements are marked up using start tags and end tags. Tags are delimited using angle brackets with the tag name in between.
The difference between start tags and end tags is that the latter includes a slash before the tag name.
Following is the example of an HTML5 element −
<p>...</p>
HTML5 tag names are case insensitive and may be written in all uppercase or mixed case, although the most common convention is to stick with lower case.
Most of the elements contain some content like <p>...</p> contains a paragraph. Some elements, however, are forbidden from containing any content at all and these are known as void elements. For example, br, hr, link and meta etc.
Here is a complete list of HTML5 Elements.

HTML5 Attributes

Elements may contain attributes that are used to set various properties of an element.
Some attributes are defined globally and can be used on any element, while others are defined for specific elements only. All attributes have a name and a value and look like as shown below in the example.
Following is the example of an HTML5 attributes which illustrates how to mark up a div element with an attribute named class using a value of "example" −
<div class="example">...</div>
Attributes may only be specified within start tags and must never be used in end tags.
HTML5 attributes are case insensitive and may be written in all upper case or mixed case, although the most common convention is to stick with lower case.
Here is a complete list of HTML5 Attributes.

HTML5 Document

The following tags have been introduced for better structure −
  • section − This tag represents a generic document or application section. It can be used together with h1-h6 to indicate the document structure.
  • article − This tag represents an independent piece of content of a document, such as a blog entry or newspaper article.
  • aside − This tag represents a piece of content that is only slightly related to the rest of the page.
  • header − This tag represents the header of a section.
  • footer − This tag represents a footer for a section and can contain information about the author, copyright information, etc.
  • nav − This tag represents a section of the document intended for navigation.
  • dialog − This tag can be used to mark up a conversation.
  • figure − This tag can be used to associate a caption together with some embedded content, such as a graphic or video.
The markup for an HTM 5 document would look like the following −
<!DOCTYPE html>
<html>

   <head>
      <meta charset="utf-8">
      <title>...</title>
   </head>
 
   <body>
      <header>...</header>
      <nav>...</nav>
  
      <article>
         <section>
            ...
         </section>
      </article>
  
      <aside>...</aside>
      <figure>...</figure> 
      <footer>...</footer>
   </body>
</html>
<!DOCTYPE html>

<html>

   <head>
      <meta charset="utf-8">
      <title>...</title>
   </head>
 
   <body>
 
      <header role="banner">
         <h1>HTML5 Document Structure Example</h1>
         <p>This page should be tried in safari, chrome or Mozila.</p>
      </header>
  
      <nav>
  
         <ul>
            <li><a href="http://www.tutorialspoint.com/html">HTML Tutorial</a></li>
            <li><a href="http://www.tutorialspoint.com/css">CSS Tutorial</a></li>
            <li><a href="http://www.tutorialspoint.com/javascript">JavaScript Tutorial</a></li>
         </ul>
   
      </nav>
  
      <article>
         <section>
            <p>Once article can have multiple sections</p>
         </section>
      </article>
  
      <aside>
         <p>This is  aside part of the web page</p>
      </aside>
      
      <figure align="right">
        <img src="/html5/images/logo.png" alt="TutorialPoint" width="200" height="100">
      </figure>
      
      <footer>
         <p>Created by <a href="http://tutorialspoint.com/">Tutorials Point</a></p>
      </footer>
  
   </body>
</html>
This will produce following result −

HTML5 - Attributes

As explained in previous chapter, elements may contain attributes that are used to set various properties of an element.
Some attributes are defined globally and can be used on any element, while others are defined for specific elements only. All attributes have a name and a value and look like as shown below in the example.
Following is the example of an HTML5 attributes which illustrates how to mark up a div element with an attribute named class using a value of "example" −
<div class="example">...</div>
Attributes may only be specified within start tags and must never be used in end tags.
HTML5 attributes are case insensitive and may be written in all uppercase or mixed case, although the most common convention is to stick with lowercase.

Standard Attributes

The attributes listed below are supported by almost all the HTML 5 tags.
Attribute Options Function
accesskey User Defined Specifies a keyboard shortcut to access an element.
align right, left, center Horizontally aligns tags
background URL Places an background image behind an element
bgcolor numeric, hexidecimal, RGB values Places a background color behind an element
class User Defined Classifies an element for use with Cascading Style Sheets.
contenteditable true, false Specifies if the user can edit the element's content or not.
contextmenu Menu id Specifies the context menu for an element.
data-XXXX User Defined Custom attributes. Authors of a HTML document can define their own attributes. Must start with "data-".
draggable true,false, auto Specifies whether or not a user is allowed to drag an element.
height Numeric Value Specifies the height of tables, images, or table cells.
hidden hidden Specifies whether element should be visible or not.
id User Defined Names an element for use with Cascading Style Sheets.
item List of elements Used to group elements.
itemprop List of items Used to group items.
spellcheck true, false Specifies if the element must have it's spelling or grammar checked.
style CSS Style sheet Specifies an inline style for an element.
subject User define id Specifies the element's corresponding item.
tabindex Tab number Specifies the tab order of an element.
title User Defined "Pop-up" title for your elements.
valign top, middle, bottom Vertically aligns tags within an HTML element.
width Numeric Value Specifies the width of tables, images, or table cells.
For a complete list of HTML5 Tags and related attributes please check reference to HTML5 Tags.

Custom Attributes

A new feature being introduced in HTML 5 is the addition of custom data attributes.
A custom data attribute starts with data- and would be named based on your requirement. Following is the simple example −
<div class="example" data-subject="physics" data-level="complex">
   ...
</div>
The above will be perfectly valid HTML5 with two custom attributes called data-subject and data-level. You would be able to get the values of these attributes using JavaScript APIs or CSS in similar way as you get for standard attributes.

HTML5 - Events

When a user visit your website, they do things like click on text and images and given links, hover over things etc. These are examples of what JavaScript calls events.
We can write our event handlers in Javascript or vbscript and you can specify these event handlers as a value of event tag attribute. The HTML5 specification defines various event attributes as listed below −
There are following attributes which can be used to trigger any javascript or vbscript code given as value, when there is any event occurs for any HTM5 element.
We would cover element specific events while discussing those elements in detail in subsequent chapters.
Attribute Value Description
offline script Triggers when the document goes offline
onabort script Triggers on an abort event
onafterprint script Triggers after the document is printed
onbeforeonload script Triggers before the document loads
onbeforeprint script Triggers before the document is printed
onblur script Triggers when the window loses focus
oncanplay script Triggers when media can start play, but might has to stop for buffering
oncanplaythrough script Triggers when media can be played to the end, without stopping for buffering
onchange script Triggers when an element changes
onclick script Triggers on a mouse click
oncontextmenu script Triggers when a context menu is triggered
ondblclick script Triggers on a mouse double-click
ondrag script Triggers when an element is dragged
ondragend script Triggers at the end of a drag operation
ondragenter script Triggers when an element has been dragged to a valid drop target
ondragleave script Triggers when an element leaves a valid drop target
ondragover script Triggers when an element is being dragged over a valid drop target
ondragstart script Triggers at the start of a drag operation
ondrop script Triggers when dragged element is being dropped
ondurationchange script Triggers when the length of the media is changed
onemptied script Triggers when a media resource element suddenly becomes empty.
onended script Triggers when media has reach the end
onerror script Triggers when an error occur
onfocus script Triggers when the window gets focus
onformchange script Triggers when a form changes
onforminput script Triggers when a form gets user input
onhaschange script Triggers when the document has change
oninput script Triggers when an element gets user input
oninvalid script Triggers when an element is invalid
onkeydown script Triggers when a key is pressed
onkeypress script Triggers when a key is pressed and released
onkeyup script Triggers when a key is released
onload script Triggers when the document loads
onloadeddata script Triggers when media data is loaded
onloadedmetadata script Triggers when the duration and other media data of a media element is loaded
onloadstart script Triggers when the browser starts to load the media data
onmessage script Triggers when the message is triggered
onmousedown script Triggers when a mouse button is pressed
onmousemove script Triggers when the mouse pointer moves
onmouseout script Triggers when the mouse pointer moves out of an element
onmouseover script Triggers when the mouse pointer moves over an element
onmouseup script Triggers when a mouse button is released
onmousewheel script Triggers when the mouse wheel is being rotated
onoffline script Triggers when the document goes offline
onoine script Triggers when the document comes online
ononline script Triggers when the document comes online
onpagehide script Triggers when the window is hidden
onpageshow script Triggers when the window becomes visible
onpause script Triggers when media data is paused
onplay script Triggers when media data is going to start playing
onplaying script Triggers when media data has start playing
onpopstate script Triggers when the window's history changes
onprogress script Triggers when the browser is fetching the media data
onratechange script Triggers when the media data's playing rate has changed
onreadystatechange script Triggers when the ready-state changes
onredo script Triggers when the document performs a redo
onresize script Triggers when the window is resized
onscroll script Triggers when an element's scrollbar is being scrolled
onseeked script Triggers when a media element's seeking attribute is no longer true, and the seeking has ended
onseeking script Triggers when a media element's seeking attribute is true, and the seeking has begun
onselect script Triggers when an element is selected
onstalled script Triggers when there is an error in fetching media data
onstorage script Triggers when a document loads
onsubmit script Triggers when a form is submitted
onsuspend script Triggers when the browser has been fetching media data, but stopped before the entire media file was fetched
ontimeupdate script Triggers when media changes its playing position
onundo script Triggers when a document performs an undo
onunload script Triggers when the user leaves the document
onvolumechange script Triggers when media changes the volume, also when volume is set to "mute"
onwaiting script Triggers when media has stopped playing, but is expected to resume

HTML5 - Web Forms 2.0

Web Forms 2.0 is an extension to the forms features found in HTML4. Form elements and attributes in HTML5 provide a greater degree of semantic mark-up than HTML4 and remove a great deal of the need for tedious scripting and styling that was required in HTML4.

The <input> element in HTML4

HTML4 input elements use the type attribute to specify the data type.HTML4 provides following types −
Type Description
text A free-form text field, nominally free of line breaks.
password A free-form text field for sensitive information, nominally free of line breaks.
checkbox A set of zero or more values from a predefined list.
radio An enumerated value.
submit A free form of button initiates form submission.
file An arbitrary file with a MIME type and optionally a file name.
image A coordinate, relative to a particular image's size, with the extra semantic that it must be the last value selected and initiates form submission.
hidden An arbitrary string that is not normally displayed to the user.
select An enumerated value, much like the radio type.
textarea A free-form text field, nominally with no line break restrictions.
button A free form of button which can initiates any event related to button.
Following is the simple example of using labels, radio buttons, and submit buttons −
...
<form action="http://example.com/cgiscript.pl" method="post">

   <p>
 
      <label for="firstname">first name: </label>
      <input type="text" id="firstname"><br />
  
      <label for="lastname">last name: </label>
      <input type="text" id="lastname"><br />
  
      <label for="email">email: </label>
      <input type="text" id="email"><br>
  
      <input type="radio" name="sex" value="male"> Male<br>
      <input type="radio" name="sex" value="female"> Female<br>
      <input type="submit" value="send"> <input type="reset">
      
   </p>
</form>
 ...

The <input> element in HTML5

Apart from the above mentioned attributes, HTML5 input elements introduced several new values for the type attribute. These are listed below.
NOTE − Try all the following example using latest version of Opera browser.
Type Description
datetime A date and time (year, month, day, hour, minute, second, fractions of a second) encoded according to ISO 8601 with the time zone set to UTC.
datetime-local A date and time (year, month, day, hour, minute, second, fractions of a second) encoded according to ISO 8601, with no time zone information.
date A date (year, month, day) encoded according to ISO 8601.
month A date consisting of a year and a month encoded according to ISO 8601.
week A date consisting of a year and a week number encoded according to ISO 8601.
time A time (hour, minute, seconds, fractional seconds) encoded according to ISO 8601.
number This accepts only numerical value. The step attribute specifies the precision, defaulting to 1.
range The range type is used for input fields that should contain a value from a range of numbers.
email This accepts only email value. This type is used for input fields that should contain an e-mail address. If you try to submit a simple text, it forces to enter only email address in email@example.com format.
url This accepts only URL value. This type is used for input fields that should contain a URL address. If you try to submit a simple text, it forces to enter only URL address either in http://www.example.com format or in http://example.com format.
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