Category Archives: javascript

JavaScript inheritance example

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JavaScript and inheritance

Almost for everybody the JavaScript way of implementing inheritance is odd. For a typical programmer it should look more C or Java like, but is not. However to give you a breve example, I’d like to make two objects, and to make the second one to inherit from the first. Thus I’d like to show how neither parent or child objects interact once they have been instanciated.

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	var parent = function() {};
	parent.prototype = {
		name : 'parent',
		m : 1,
		a : function() {
			console.log(this.name + ': ' + this.m);
		},
		setM : function( value ) {
			this.m = value;
		}
	};
 
	var child = function() {};
	child.prototype = new parent;
	child.prototype.name = 'child';
 
	var parentObj = new parent();
	var childObj = new child();
 
	parentObj.a();
	parentObj.setM(12);
 
	childObj.a();
	childObj.setM(3);
 
	parentObj.a();
	childObj.a();

However this describes the ability to make complex JavaScript inheritance patterns. The complete source’s here.

jQuery localStorage plugin (alpha)

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After submitting the HTML5 localStorage wrap plugin for jQuery, there comes the new version, hopefully more stable and reliable!

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(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;
 
      if (typeof lifetime == 'undefined')
         lifetime = 60000;
 
      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) {
      if (!supported)
         return false;
 
      var time = new Date();
      if (time.getTime() - ls.getItem('meta_ct_'+key) > ls.getItem('meta_lt_'+key)) {
         ls.removeItem(key);
         ls.removeItem('meta_ct_'+key);
         ls.removeItem('meta_lt_'+key);
         return false;
      }
      return JSON.parse(ls.getItem(key));
   };
 
   this.removeItem = function(key) {
      if (!supported)
         return false;
 
      ls.removeItem(key);
      ls.removeItem('meta_ct_'+key);
      ls.removeItem('meta_lt_'+key);
      return true;
   };
 
   jQuery.localStorage = this;
 
})(jQuery);
 
if (!$.localStorage.getItem('test')) {
   $.localStorage.setItem('test', ['stoimen'], 5000);
   console.log('dynamic');
} else {
   console.log('from cache');
}

jQuery localStorage plugin

javascript, , ,

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.