HTML5 Web Storage

HTML5 web storage, a better local storage than cookies.

What is HTML5 Web Storage?

With HTML5, web pages can store data locally within the user's browser.
Earlier, this was done with cookies. However, Web Storage is more secure and faster. The data is not included with every server request, but used ONLY when asked for. It is also possible to store large amounts of data, without affecting the website's performance.
The data is stored in key/value pairs, and a web page can only access data stored by itself.

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Browser Support

Web storage is supported in Internet Explorer 8+, Firefox, Opera, Chrome, and Safari.
Note: Internet Explorer 7 and earlier versions, do not support web storage.

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localStorage and sessionStorage 

There are two new objects for storing data on the client:

• localStorage - stores data with no expiration date
• sessionStorage - stores data for one session

Before using web storage, check browser support for localStorage and sessionStorage:

if(typeof(Storage)!=="undefined")
  {
  // Yes! localStorage and sessionStorage support!
  // Some code.....
  }
else
  {
  // Sorry! No web storage support..
  }

---

The local Storage Object

The local Storage object stores the data with no expiration date. The data will not be deleted when the browser is closed, and will be available the next day, week, or year.

Example

localStorage.lastname="Smith";
document.getElementById("result").innerHTML="Last name: "
+ localStorage.lastname;

Try it yourself »

Example explained:

• Create a localStorage key/value pair with key="lastname" and value="Smith"
• Retrieve the value of the "lastname" key and insert it into the element with id="result"

Tip: Key/value pairs are always stored as strings. Remember to convert them to another format when needed.
The following example counts the number of times a user has clicked a button. In this code the value string is converted to a number to be able to increase the counter:

Example

if (localStorage.clickcount)
  {
  localStorage.clickcount=Number(localStorage.clickcount)+1;
  }
else
  {
  localStorage.clickcount=1;
  }
document.getElementById("result").innerHTML="You have clicked the button " + localStorage.clickcount + " time(s).";

Try it yourself »

---

The sessionStorage Object

The sessionStorage object is equal to the localStorage object, except that it stores the data for only one session. The data is deleted when the user closes the browser window.
The following example counts the number of times a user has clicked a button, in the current session:

Example

if (sessionStorage.clickcount)
  {
  sessionStorage.clickcount=Number(sessionStorage.clickcount)+1;
  }
else
  {
  sessionStorage.clickcount=1;
  }
document.getElementById("result").innerHTML="You have clicked the button " + sessionStorage.clickcount + " time(s) in this session.";

Try it yourself » Refferenced from W3school »

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HTML5 Server-Sent Events

What is the Web workers
 
A server-sent event is when a web page automatically gets updates from a server.
This was also possible before, but the web page would have to ask if any updates were available. With server-sent events, the updates come automatically.
Examples: Facebook/Twitter updates, stock price updates, news feeds, sport results, etc.


 ΙΕ not Support.

var source=new EventSource("sample.php");
source.onmessage=function(event)
  {
  document.getElementById("result").innerHTML+=event.data + "
";
  };

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HTML5 Web Workers

What is the Web workers
  A web worker is a JavaScript that runs in the background, independently of other scripts, without affecting the performance of the page. You can continue to do whatever you want: clicking, selecting things, etc., while the web worker runs in the background.


 ΙΕ not Support.

<button onclick="startWorker()">Start Worker</button>
<button onclick="stopWorker()">Stop Worker</button>

<script>
var w;

function startWorker()
{
if(typeof(Worker)!=="undefined")
  {
  if(typeof(w)=="undefined")
  {
  w=new Worker("demo_workers.js");
  }
  w.onmessage = function (event) {
    document.getElementById("result").innerHTML=event.data;
    };
  }
else
  {
  document.getElementById("result").innerHTML="Sorry, your browser does not support Web Workers...";
  }
}

function stopWorker()
{
w.terminate();
}
</script>

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html5 Figure & Figcaption

  
  
this is the figure caption 

A cheeky macaque, Lower Kintaganban River, Borneo. Original by Richard Clark

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