Tag Archives: javascript

I recently read The Principles of Object-Oriented JavaScript by Nicholas Zakas and was enthralled by his patterns for prototypal inheritance of both instantiated and non-instantiated objects.   As I put each of these patterns to practice I noticed an interesting “discrepancy” between the the way each was linked to its parent.  I thought it was interesting enough for me to dig into, so it might make an interesting blog post.

Example 1: Instantiated Object Inheritance

In the example below, we create our parent class “Animal” which is created via the function method.  We attach a simple method to the prototype which retrieves the private “species” variable.

Then we create a “Dog” subclass by creating it via the function method, then linking the two classes with

Dog.prototype = Object.create(Animal.prototype);

This overrides the default Dog prototype with the Animal prototype, resulting in the correct prototype chain.  Here is a very abbreviated version of the prototype chain.

Screen Shot 2014-05-14 at 4.43.33 PM

Note the very important constructor attachment required after we override the prototype.

Dog.prototype.constructor = Dog;

Pretty common sequence to chain these two classes together.  Any changes made to Animal will get automatically chained to Dog.  Now let’s take a look at the non-instantiated example.

Example 2: Non-instantiated Object Inheritance

In this example we’ll use a IIFE (Immediately-invoked functional expression) to create our parent class, with our retrieval function as above.  This pattern is common for singleton type use cases.

Now notice how we chain the prototypes of the Animal and Dog classes, specifically what is passed to the Object.create() function.

var myDog = Object.create(animal);

No mention of a prototype!  Why not?  Why are we attaching the object itself instead of its prototype?

The reason is because of what Animal is in this second example.  In example 1, Animal was created via the function literal resulting in an object with a full prototype chain inherited from Function. In the second example, animal was created via the inline object declaration “{}” resulting in an object with a prototype of “null”. To put it shortly, an object only has a prototype property if it was created via function literal.

Screen Shot 2014-05-14 at 4.43.40 PM

So if you called the following code, you would get a big fat error because animal has no prototype property.

var myDog = Object.create(animal.prototype); //TypeError

So in example 2, the Animal object itself is what gets chained to myDog. MyDog  can now add its own methods without modifying the original Animal object.

 

I occasionally read through discussion boards that show off various artwork, but often find myself sifting through pages of text till I finally find the images I’m looking for.  So rather than continually sift by hand, I build this tool to ease the process.

DEMO

Here’s how it works. First off, rather than download all images to my server and sort them out there, we simply generate a new “lens” on the existing page, then let the client’s browser verify the images in javascript.  Once we have the images loaded, we can remove all images smaller than 120×120 pixels (avatars and such) and display the results in a easy to view format.  Lastly, we show the original size artwork scaled down, so that we can easily “right click to save.” The other feature I threw in was the ability to navigate by pages, so if the discussion board your reading supports paging, the extractor should figure it out and let you view pages by using the right and left arrows.

Need to check if your users are using a “supported” browser for your site? Don’t like how jQuery handles browser version numbers and chrome. Here’s a bit of javascript to make your life easier by putting version numbers in human readable format. Just update the numbers to match what you consider “supportable” for your site.

 function is_supported_browser()
 {
 var userAgent = navigator.userAgent.toLowerCase();

// Is this a version of IE?
 if($j.browser.msie)
 {
 userAgent = $j.browser.version;
 version = userAgent.substring(0,userAgent.indexOf('.'));
 if ( version >= 8 ) return true;
 }

// Is this a version of Chrome?
 $j.browser.chrome = /chrome/.test(navigator.userAgent.toLowerCase());
 if($j.browser.chrome)
 {
 userAgent = userAgent.substring(userAgent.indexOf('chrome/') +7);
 version = userAgent.substring(0,userAgent.indexOf('.'));
 if (version >= 13) return true;
 }

// Is this a version of Safari?
 if($j.browser.safari)
 {
 userAgent = userAgent.substring(userAgent.indexOf('version/') +8);
 version = userAgent.substring(0,userAgent.indexOf('.'));
 if (version >= 5) return true;
 }

// Is this a version of firefox?
 if($j.browser.mozilla && navigator.userAgent.toLowerCase().indexOf('firefox') != -1)
 {
 userAgent = userAgent.substring(userAgent.indexOf('firefox/') +8);
 version = userAgent.substring(0,userAgent.indexOf('.'));
 if (version >= '3.6') return true;
 }
 return false;
 }
 

So I’ve had quite a few questions about how I do AJAX caching in Titanium Appcelerator. So, here’s my solution.

First, I needed some persistent storage with a very general structure. I could have gone with flat files, but I decided to make use of the built-in SQLite engine, so that I could easily access entries and delete old data.

Database

var db_conn = Ti.Database.open('app_db1');
db_conn.execute('CREATE TABLE IF NOT EXISTS `remote_cache`
                 (key TEXT, type TEXT, valid_till TEXT, value TEXT,
                 PRIMARY KEY (key, type))');

Next, I need a wrapper class for my ajax calls. Note the “get” function which is the main function call. Here is the signature and explaination:

get: function (url, params, type, valid_for, callback, skip_cache)

  • url : string : the full url to call
  • params : object : a simple object with name/value parse for POST variables
  • type : string : the cache domain for this call. Usefull for clearing all cache data for a specific domain
  • valid_for : date string : the amount of time the cache should remain valid for
  • callback : function : the function to call on completion or fail of the request
  • skip_cache : boolean : an option to bypass the cache and perform write through

AJAX Class


var ajax =
{
	http_conn: Ti.Network.createHTTPClient(),
	url:'',
	type:'',
	params:{},
	key:'',
	valid_for: '+1 hour',
	callback: null,
	debug:true,
	get: function (url, params, type, valid_for, callback, skip_cache)
	{
		this.key = MD5(url + '|' +   JSON.stringify(params));
		this.url = url;
		this.params = params;
		this.valid_for = valid_for;
		this.type = type;

		this.callback = callback;

		if (ajax.debug) Titanium.API.info('Ajax Call');
		if (skip_cache)
		{
			this.remote_grab();
		}
		else if (!this.local_grab())
		{
			this.remote_grab();
		}

	},
	abort : function ()
	{
		this.http_conn.abort();
	},

	local_grab: function ()
	{
		if (ajax.debug) Titanium.API.info('Checking Local key:' + this.key);

		var rows = db_conn.execute('SELECT valid_till, value FROM remote_cache WHERE key = ? AND type = ? AND valid_till > datetime(\'now\')',  this.key, this.type);//, '', '+this.valid_for+')');//',  this.key, 'date(\'now\', '+this.valid_for+')');
		var result = false;
		if (rows.isValidRow())
		{
			if (ajax.debug) Titanium.API.info('Local cache found with expiration:' + rows.fieldByName('valid_till'));
			var result = JSON.parse(rows.fieldByName('value'));
			rows.close();

			this.callback(result);
			result = true;
		}
		rows.close();
		return result;
	},

	remote_grab: function ()
	{
		if (ajax.debug) Titanium.API.info('Calling Remote: ' + this.url + ' - PARAMS: '+ JSON.stringify(this.params));

		this.abort();
		this.http_conn.setTimeout(10000);

		// catch errors
		this.http_conn.onerror = function(e)
		{
			//alert('Call failed');
			ajax.callback({result:false});
			Ti.API.info(e);
		};

		// open connection
		this.http_conn.open('POST', this.url);

		// act on response
		var key = this.key;
		var valid_for = this.valid_for;
		var callback = this.callback;
		var type = this.type;

		this.http_conn.onload = function()
		{
			if (ajax.debug) Titanium.API.info('Response from server:' + this.responseText);
			if (this.responseText != 'null')
			{
				var response = JSON.parse(this.responseText);
				if (response.result == true || (response && response.length > 0))
				{
					ajax.update_local(key, type, valid_for, response);
					callback(response);
				}
				else if (response.result == false && response.error  && response.error.length > 0)
				{
					callback({result:false,error:response.error});
				}
				else
				{
					callback({result:false,error:'Invalid Result (1)'});
				}
			}
			else
			{
				callback({result:false,error:'Invalid Result (2)'});
			}
		};

		// Send the HTTP request
		this.http_conn.send(this.params);

	},

	update_local: function (key, type, valid_for, response)
	{
		if (ajax.debug) Ti.API.info('Updating Cache: KEY: ' + key + ' TYPE: ' + type +' - FOR: '+valid_for+', ' + JSON.stringify(response));
		db_conn.execute('DELETE FROM remote_cache WHERE (valid_till <= datetime(\'now\') OR key = ?) AND type = ?', key, type);
		db_conn.execute('INSERT INTO remote_cache ( key, type, valid_till, value ) VALUES(?,?,datetime(\'now\',?),?)',key, type, valid_for, JSON.stringify(response));
	}
};

I recently began using Titanium Appcelerator to build an iPhone app for WorthMonkey. One of the features I love in any application, is the ability to search a table using remote data. However, this is very difficult to pull off in Appcelerator, because it’s table search work only on local data. So here’s how I got around that limitation to make a true remote search table.

First, obviously it quite easy to add a search bar to a table, so I did that then attached a listener on the “change” event. But when you attempt to do your remote call here, the built in filter fires first and overlays the current table, so updating the table contents afterward is of no help. So, the trick is to fire the filter event again, AFTER you’ve filled the table. So on line 70, I tell the filter to fire again, and on line 24 I put a check in to make sure we don’t start infinite calls. Enjoy!

//SEARCH BAR
var search = Titanium.UI.createSearchBar({
	barColor:'#77B121',
	height:43,
	hintText:'What\'s It Worth?',
	top:0
});

//AUTOCOMPLETE TABLE
var table_data = [];
var autocomplete_table = Titanium.UI.createTableView({
	search: search,
	scrollable: true,
	top:0
});
win.add(autocomplete_table);

//
// SEARCH BAR EVENTS
//
var last_search = null;
search.addEventListener('change', function(e)
{
	if (search.value.length > 2 && search.value !=  last_search)
	{
		clearTimeout(timers['autocomplete']);
		timers['autocomplete'] = setTimeout(function()
		{
			last_search =search.value;
			auto_complete(search.value);
		}, 300);
	}
	return false;
});

function auto_complete(search_term)
{
	if (search_term.length > 2)
	{
		var url = 'YOURURL' + escape( search_term);
		var ajax_cache_domain = 'autocomplete';
		var params = {};
		var cache_for = '+7 days';
		ajax.get(url, params, ajax_cache_domain, cache_for, function (response)
		{
			if (typeof(response) == 'object')
			{
				var list = response;
				// Empty array &quot;data&quot; for our tableview
				table_data = [];

				for (var i = 0; i < list.length; i++)
				{
					//Ti.API.info('row data - ' + data[i].value);
					var row = Ti.UI.createTableViewRow(
					{
						height: 40,
						title: list[i].value.replace(/^\s+|\s+$/g,""),
						hasDetail:true
					});

					// apply rows to data array
					table_data.push(row);

				};

				// set data into tableView

				autocomplete_table.setData(table_data);
				search.value = search.value;
			}
			else
			{
				alert(response.error);
			}

		});
	}
}

Original Post

So I wanted to build a link parser like the one on Facebook, but didn’t find one that suited me. So I built one. My code is based off the code found here, but I rewrote much of it to be cleaner and to return JSON rather than HTML.

Code Change – Feb 2nd, 2011
Added some refinements to the cleaning mechanism and greatly speed up image parser.

HTML

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.4/jquery.min.js"></script>
<style>
	#atc_bar{width:500px;}
	#attach_content{border:1px solid #ccc;padding:10px;margin-top:10px;}
	#atc_images {width:100px;height:120px;overflow:hidden;float:left;}
	#atc_info {width:350px;float:left;height:100px;text-align:left; padding:10px;}
	#atc_title {font-size:14px;display:block;}
	#atc_url {font-size:10px;display:block;}
	#atc_desc {font-size:12px;}
	#atc_total_image_nav{float:left;padding-left:20px}
	#atc_total_images_info{float:left;padding:4px 10px;font-size:12px;}
</style>
<br /><br /><br /><br />

<div align="center">
	<h1>Parse a Link Like Facebook with PHP and Jquery</h1>
	<div id="atc_bar" align="center">
		Paste Link Here: <input type="text" name="url" size="40" id="url" value="" />
		<input type="button" name="attach" value="Parse" id="attach" />
		<input type="hidden" name="cur_image" id="cur_image" />
		<div id="loader">

			<div align="center" id="atc_loading" style="display:none"><img src="load.gif" alt="Loading" /></div>
			<div id="attach_content" style="display:none">
				<div id="atc_images"></div>
				<div id="atc_info">

					<label id="atc_title"></label>
					<label id="atc_url"></label>
					<br clear="all" />
					<label id="atc_desc"></label>
					<br clear="all" />
				</div>
				<div id="atc_total_image_nav" >
					<a href="#" id="prev"><img src="prev.png"  alt="Prev" border="0" /></a><a href="#" id="next"><img src="next.png" alt="Next" border="0" /></a>
				</div>

				<div id="atc_total_images_info" >
					Showing <span id="cur_image_num">1</span> of <span id="atc_total_images">1</span> images
				</div>
				<br clear="all" />
			</div>
		</div>
		<br clear="all" />
	</div>
</div>

JavaScript


<script>

	$(document).ready(function(){

		// delete event
		$('#attach').bind("click", parse_link);

		function parse_link ()
		{
			if(!isValidURL($('#url').val()))
			{
				alert('Please enter a valid url.');
				return false;
			}
			else
			{
				$('#atc_loading').show();
				$('#atc_url').html($('#url').val());
				$.post("fetch.php?url="+escape($('#url').val()), {}, function(response){

					//Set Content
					$('#atc_title').html(response.title);
					$('#atc_desc').html(response.description);
					$('#atc_price').html(response.price);

					$('#atc_total_images').html(response.total_images);

					$('#atc_images').html(' ');
					$.each(response.images, function (a, b)
					{
						$('#atc_images').append('<img src="'+b.img+'" width="100" id="'+(a+1)+'">');
					});
					$('#atc_images img').hide();

					//Flip Viewable Content
					$('#attach_content').fadeIn('slow');
					$('#atc_loading').hide();

					//Show first image
					$('img#1').fadeIn();
					$('#cur_image').val(1);
					$('#cur_image_num').html(1);

					// next image
					$('#next').unbind('click');
					$('#next').bind("click", function(){

						var total_images = parseInt($('#atc_total_images').html());
						if (total_images > 0)
						{
							var index = $('#cur_image').val();
							$('img#'+index).hide();
							if(index < total_images)
							{
								new_index = parseInt(index)+parseInt(1);
							}
							else
							{
								new_index = 1;
							}

							$('#cur_image').val(new_index);
							$('#cur_image_num').html(new_index);
							$('img#'+new_index).show();
						}
					});

					// prev image
					$('#prev').unbind('click');
					$('#prev').bind("click", function(){

						var total_images = parseInt($('#atc_total_images').html());
						if (total_images > 0)
						{
							var index = $('#cur_image').val();
							$('img#'+index).hide();
							if(index > 1)
							{
								new_index = parseInt(index)-parseInt(1);;
							}
							else
							{
								new_index = total_images;
							}

							$('#cur_image').val(new_index);
							$('#cur_image_num').html(new_index);
							$('img#'+new_index).show();
					 	}
					});
				});
			}
		};
	});

	function isValidURL(url)
	{
		var RegExp = /(ftp|http|https):\/\/(\w+:{0,1}\w*@)?(\S+)(:[0-9]+)?(\/|\/([\w#!:.?+=&%@!\-\/]))?/;

		if(RegExp.test(url)){
			return true;
		}else{
			return false;
		}
	}
</script>

PHP

$url = urldecode($_REQUEST['url']);
$url = checkValues($url);
$return_array = array();

$base_url = substr($url,0, strpos($url, "/",8));
$relative_url = substr($url,0, strrpos($url, "/")+1);

// Get Data
$cc = new cURL();
$string = $cc->get($url);
$string = str_replace(array("\n","\r","\t",'</span>','</div>'), '', $string);

$string = preg_replace('/(<(div|span)\s[^>]+\s?>)/',  '', $string);
if (mb_detect_encoding($string, "UTF-8") != "UTF-8")
	$string = utf8_encode($string);

// Parse Title
$nodes = extract_tags( $string, 'title' );
$return_array['title'] = trim($nodes[0]['contents']);

// Parse Base
$base_override = false;
$base_regex = '/<base[^>]*'.'href=[\"|\'](.*)[\"|\']/Ui';
preg_match_all($base_regex, $string, $base_match, PREG_PATTERN_ORDER);
if(strlen($base_match[1][0]) > 0)
{
	$base_url = $base_match[1][0];
	$base_override = true;
}

// Parse Description
$return_array['description'] = '';
$nodes = extract_tags( $string, 'meta' );
foreach($nodes as $node)
{
	if (strtolower($node['attributes']['name']) == 'description')
		$return_array['description'] = trim($node['attributes']['content']);
}

// Parse Images
$images_array = extract_tags( $string, 'img' );
$images = array();
for ($i=0;$i<=sizeof($images_array);$i++)
{
	$img = trim(@$images_array[$i]['attributes']['src']);
	$width = preg_replace("/[^0-9.]/", '', $images_array[$i]['attributes']['width']);
	$height = preg_replace("/[^0-9.]/", '', $images_array[$i]['attributes']['height']);

	$ext = trim(pathinfo($img, PATHINFO_EXTENSION));

	if($img && $ext != 'gif')
	{
		if (substr($img,0,7) == 'http://')
			;
		else	if (substr($img,0,1) == '/' || $base_override)
			$img = $base_url . $img;
		else
			$img = $relative_url . $img;

		if ($width == '' && $height == '')
		{
			$details = @getimagesize($img);

			if(is_array($details))
			{
				list($width, $height, $type, $attr) = $details;
			}
		}
		$width = intval($width);
		$height = intval($height);

		if ($width > 199 || $height > 199 )
		{
			if (
				(($width > 0 && $height > 0 && (($width / $height) < 3) && (($width / $height) > .2))
					|| ($width > 0 && $height == 0 && $width < 700)
					|| ($width == 0 && $height > 0 && $height < 700)
				)
				&& strpos($img, 'logo') === false )
			{
				$images[] = array("img" => $img, "width" => $width, "height" => $height, 'area' =>  ($width * $height),'offset' => $images_array[$i]['offset']);
			}
		}

	}
}
$return_array['images'] = array_values(($images));
$return_array['total_images'] = count($return_array['images']);

header('Cache-Control: no-cache, must-revalidate');
header('Expires: Mon, 26 Jul 1997 05:00:00 GMT');
header('Content-type: application/json');

echo json_encode($return_array);
exit;