Tag Archives: HTML 5

HTML5 geolocation – What If the User Doesn’t Share His Position?

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HTML5 Geolocation

So far we were used to expect something like this from our mobile phones with built-in GPS support. Every image or video clip then was automatically “tagged” with latitude & longitude geo data. With HTML5 coming features we discover new cool things we can do with our browsers. Such cool thing is the geolocation.

Geo Location

Support

As you may guess not every browser is supporting these HTML5 features, but out in the web there is quite good collection of tables comparing different browsers and their support level.

Firefox

This – as expected is a browser that supports this geo tagging. First of all you’ve to allow your browser to use your geo coordinates, as this can be private information.

Browser GEO Location

Once you do it you can access the geo coordinates, which by the way are quite accurate, with JavaScript.

What if you don’t share your position?

What happens if you don’t want to share your position? Actually I ran in this situation and as my application waited the coordinates – it was completely blocked.

The examples doesn’t show you something special. They simply describe how to get the coordinates, but doesn’t tell you what if the user doesn’t click on the “share” button.

if (!!navigator.geolocation) {
        navigator.geolocation.getCurrentPosition(getPos);
}
...
 
function getPos(position) 
{
    position.coords.latitude;
    position.coords.longitude;
}

Of course getPos() can be simply an anonymous function:

if (!!navigator.geolocation) {
        navigator.geolocation.getCurrentPosition(function(position) {
            position.coords.latitude;
            position.coords.longitude;
        });
}

Only the Firefox documentation tells you how to handle errors, simply add one more parameter – callback, for getCurrentPosition() method:

if (!!navigator.geolocation) {
        navigator.geolocation.getCurrentPosition(getPos, onError);
}
...
 
function getPos(position) 
{
    position.coords.latitude;
    position.coords.longitude;
}
 
function onError()
{
   // handle error
}

Now you know where you don’t want to be.

Map Marker

Secure localStorage? Now that’s a good question!

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Nicholas Zakas posted today a very very interesting post about one of the most interesting and useful features in HTML5 – localStorage. What’s really impressing is that everybody’s using it, including me, with no fear of security. But security is never strong enough, so it’s quite interesting to listen up the guru!

I recently posted a localStorage wrapper for jQuery in form of a simple plugin. What I miss there is the security.

Definitely I’ve to change it a bit!

HTML5 video support. Detecting, playing and progressive enhancement!

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HTML5 video

HTML5 is mentioned as entirely new “thing” out in the web, but what it actually means is rather a collection of new, unknown for the current HTML version, features. One of the most interesting and used things in HTML5 are the support of a video in a entirely new “video” tag. Until now the playing of a video was either with Flash player or with Quick Time. But in both cases it relied on a third party plugins. Of course normally the question about performance was inevitable. Which is faster? But imagine we didn’t have the IMG tag? This give you the answer – using third party plugins always slows down the page, and today most of the web is based on video sharing and therefore the browsers become slower!

Performance of HTML5 video tag against Flash video players

As I mentioned above the performance of HTML5 video should be way better than the performance of any Flash video player. To be more precise I’ll reference an article from ajaxian.com, where the author points on his turn an interesting presentation. Indeed the performance of HTML5 video was way, way better:

But sometimes this doesn’t resolves all the problems. Normally with this “new” technique of putting a video into the page, come some additional issues.

First of all there are many codecs that the browser should support and almost always there is something “your” browser don’t support. That makes the task bigger. Now you should support more and more video file formats for the different browsers. And yet another problem is the detection of this codec support.

Detection and integration

Lucky enough, I found a great article and tutorial describing how to integrate HTML5 video with progressive enhancement. First of all you can check for it’s support than downgrade to Quick Time and Flash and if the client doesn’t support even that – render an image.

You can find the source here.

Thanks to this technique you can fully integrate new video tag into your page. Remember that most of the clients for sure will be happy to watch video in a more user friendly manner.

jQuery localStorage plugin

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I’ve decided to wrap the functionality of HTML5 localStorage in a jQuery plugin, with the simple functionality of a lifetime period for every cache. I’m going to post only the pre-release with the idea to clean up the code in the recent future.

(function(jQuery) {

   var supported = true;
   if (typeof localStorage == 'undefined' || typeof JSON == 'undefined')
      supported = false;
   else
      var ls = localStorage;

   this.setItem = function(key, value, lifetime) {
      if (!supported)
         return false;

      ls.setItem(key, JSON.stringify(value));
      var time = new Date();
      ls.setItem('meta_ct_'+key, time.getTime());
      ls.setItem('meta_lt_'+key, lifetime);
   };

   this.getItem = function(key) {
      var time = new Date();
      if (!supported || time.getTime() - ls.getItem('meta_ct_'+key) > ls.getItem('meta_lt_'+key))
         return false;
      return JSON.parse(ls.getItem(key));
   };

   this.removeItem = function(key) {
      return supported && ls.removeItem(key);
   };

   jQuery.localStorage = this;

})(jQuery);

if (!$.localStorage.getItem('test')) {
   $.localStorage.setItem('test', ['stoimen'], 600000);
   alert('dynamic');
} else {
   alert('from cache');
}

Any feedback is welcome! Yet again the code isn’t tested at all.

Storing JavaScript objects in html5 localStorage

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There is a rising new age of HTML5, which comes with very nice features as video tag and localStorage. What localStorage is? In fact we have been waiting for long time to have something that give us the power of storing more and more on the client side. That’s because the net is becoming larger and therefore heavy.

Imagine if you have the possibility to store large JSON returned from an AJAX call on the client. That’s now reality with the localStorage object in HTML5 and it can be accessed with something like this code:

localStorage.setItem(key, value);
alert(localStorage.getItem(key));

Can we store entire objects?

Yes there is a way extending a bit the logic of the code above. The localStorage in fact stores only strings, but what about arrays and objects. You can additionally use JSON global objects and its two methods – stringify and parse:

var a = JSON.stringify({name:'obj'});
alert(JSON.parse(a));

Do browsers support all that?

Of course … not! localStorage is supported by Firefox 3.5+, Chrome 2+, Safari 4+ and MSIE 8+. The solution is not to rely on browser version, but to check for object existence, and than to combine both techniques:

localStorage.setItem('a', JSON.stringify({ name : 'obj' }));
alert(JSON.parse(localStorage.getItem('a')));