Web Application Developers Toolbox

What are the weaknesses of developing a web application in react instead of using jQuery with html5 and a python backend ?

2026-01-27T17:36:24.300-08:00

Weaknesses of Developing a Web Application in React vs. jQuery with HTML5 and Python Backend

When comparing React (a JavaScript library for building user interfaces) to a more traditional stack like jQuery combined with plain HTML5 for the frontend and a Python backend (e.g., using Flask, Django, or FastAPI), React offers powerful features for complex, interactive UIs.

However, it comes with several drawbacks, especially for simpler applications or teams with specific constraints. Below, I'll outline the key weaknesses of choosing React over the jQuery/HTML5 approach. Note that the backend (Python) is largely agnostic here, as both frontends can integrate with it via APIs (e.g., REST or GraphQL), but the differences are primarily in frontend development, maintenance, and performance.

1. Steeper Learning Curve and Complexity

React introduces concepts like components, state management (e.g., useState, Redux), props, lifecycle methods/hooks, and JSX (a syntax extension for JavaScript). This can be overwhelming for beginners or teams accustomed to imperative programming.

In contrast, jQuery focuses on simple DOM manipulation (e.g., $('selector').click(...)), which aligns closely with vanilla JavaScript and HTML5. Developers can start building interactive elements quickly without learning a new paradigm.

Impact: For small teams or projects with junior developers, this leads to longer onboarding times and potential bugs from misuse of React's abstractions. jQuery/HTML5 is more straightforward for quick prototypes or static-ish sites.

2. Increased Boilerplate and Tooling Overhead

React apps often require a build setup with tools like Create React App, webpack, Babel, or Vite for transpiling JSX and managing modules. This adds configuration complexity and dependencies.

jQuery can be included via a simple <script> tag in HTML5, with no build step needed. You write HTML, CSS, and JavaScript directly, making it lightweight for server-rendered pages from a Python backend.

Impact: Development workflows in React involve more setup time, debugging build issues, and managing a larger node_modules folder. This is overkill for apps that don't need single-page application (SPA) features.

3. Larger Bundle Size and Initial Load Times

React's library (about 100-150KB minified) plus any dependencies (e.g., React Router, state libraries) can result in larger JavaScript bundles. Even with code-splitting, the initial download can be heavier.

jQuery is tiny (~30KB minified/gzipped) and can be loaded conditionally. HTML5 with jQuery often relies on server-side rendering from Python, reducing client-side JavaScript needs.

Impact: Slower page loads on low-bandwidth connections or mobile devices. React apps may require optimizations like lazy loading, which add more complexity, whereas jQuery apps load faster out of the box.

4. Performance Overhead in Certain Scenarios

React's virtual DOM reconciliation is efficient for frequent updates but introduces overhead for simple interactions. Re-renders can cascade if not managed well (e.g., without memoization).

jQuery directly manipulates the real DOM, which is faster for one-off changes or small-scale apps without heavy state.

Impact: For apps with minimal interactivity (e.g., forms, basic animations), React might consume more CPU/memory. This is noticeable in resource-constrained environments, though React shines in complex UIs.

5. SEO and Accessibility ChallengesClient-side rendering in React can hinder search engine crawling unless you implement server-side rendering (SSR) with tools like Next.js, which adds significant complexity and requires Node.js integration with your Python backend.

jQuery/HTML5 apps are typically server-rendered by Python frameworks, making them inherently SEO-friendly and accessible (e.g., semantic HTML is easier to maintain without JSX).

Impact: Extra effort for React to achieve good SEO (e.g., handling hydration, pre-rendering), and potential accessibility pitfalls if components aren't built with ARIA in mind. jQuery encourages progressive enhancement, starting from accessible HTML.

6. Rapid Ecosystem Changes and Maintenance Burden

The React ecosystem evolves quickly, with frequent updates, deprecations (e.g., class components vs. hooks), and a vast array of third-party libraries that may break compatibility.

jQuery has been stable for years, with a mature API that's backward-compatible. HTML5 standards change slowly, and Python backends like Django provide long-term support.

Impact: Higher long-term maintenance costs in React due to refactoring for new best practices or vulnerabilities in dependencies. jQuery apps are easier to maintain over time, especially for legacy systems.

7. Over-Abstraction for Simple Applications

React encourages component-based architecture, which is great for scalability but unnecessary for basic sites (e.g., blogs, dashboards with light interactivity).

jQuery with HTML5 allows direct, imperative code that's easier to reason about for small scopes, integrating seamlessly with Python-templated HTML (e.g., Jinja2 in Flask).

Impact: React can lead to "over-engineering," where simple tasks become verbose. It's less suitable for multi-page applications (MPAs) without additional routing libraries, while jQuery excels in hybrid server/client setups.

8. Debugging and Testing Complexity

Debugging React involves tools like React DevTools, tracing re-renders, and handling async effects. Testing requires libraries like Jest or React Testing Library.

jQuery code is often easier to debug with browser tools alone, and unit tests can be simpler without mocking virtual DOM.

Impact: More time spent on testing setups in React, especially for stateful components. This can slow down iteration in fast-paced projects.

When React Might Still Be PreferableWhile these are weaknesses, React excels in large-scale SPAs with real-time updates (e.g., via WebSockets with a Python backend like Django Channels). If your app involves heavy user interactions, reusable UI components, or integration with modern JS ecosystems, the trade-offs might be worth it. For simpler, content-driven sites, jQuery/HTML5 with Python is often more efficient.

Windows recovery drive

2022-05-15T22:05:00.003-07:00

There might be times when you can’t actually get into your Windows Laptop. And while Windows has great recovery tools built in, at such time you can’t access the recovery tools in the normal way.

That means you can’t roll back or reinstall Windows the normal way either.

As a safety net should something go seriously wrong with your PC, youmust create a Windows recovery drive on a spare USB stick.

How?

Open the Start menu, and search for “create a recovery drive”. This will bring up the right utility.

Follow the instructions on screen to copy over the necessary files to your chosen USB drive, but note that these files won’t include your personal files and data.

If disaster strikes, you’ll need to boot up from your recovery drive.

This is usually done by holding down the Delete or F8 keys while your PC starts.

Opt to boot from your USB drive, then pick Troubleshoot > Advanced Options > Recover from a drive to get Windows reinstalled.

Rename an Android project in Eclipse

2014-03-09T10:06:00.000-07:00

Right click the project, and press F2.
You will get a Dialog box which will let you rename the project alongwith the option to update references

Alternatively,

Right click on your project
In the menu that menu that appears, Select "Refactor"
In the menu that appears, Select "Rename"
You will get a Dialog box which will let you rename the project alongwith the option to update references

Setting Up Name Based Virtual Hosting in Apache on Ubuntu

2013-08-24T15:42:00.000-07:00

Apache is by far the most popluar web server out there. Installing apache on a Ubuntu machine is straightfoward. However, whats the use of it if we cant make it run multiple sites.

Virtual Hosts are used to run more than one site off of a single IP address. If you want to be able to handle more than one domain with one web server, you'll need to set up a virtual host for each. Here I will show you how to work with Virtual Hosts by setting up 2 different sites on a single apache installation using virtual hosts.

As an example, let us assume we are setting up 2 sites www.testwadt.com and www.testwadt.net

Create 2 separate folders where we will place the files which will serve the 2 sites. Let do this in the /var/www folder

mkdir /var/www/testwadt_com
mkdir /var/www/testwadt_net

Now for each of the 2 domains, put the files in the respective folders created for the same

Also create a log folder in each of the 2 folder created above
mkdir /var/www/testwadt_com/log
mkdir /var/www/testwadt_net/log

Now we need to define to Apache that we’re using name based virtual hosting instead of IP based. You can append the following line to your /etc/apache2/apache2.conf to define this:
NameVirtualHost ip.address:port

typically this would be
NameVirtualHost :80

The next step is to set up Virtual Hosts. Each virtual host needs its own file in the /etc/apache2/sites-available/ directory.
This allows for a clear and specific per-site configuration.

So lets create files for the two sites we wish to host: testwadt.com and testwadt.net

First lets create a file testwadt.com in /etc/apache2/sites-available

vi /etc/apache2/sites-available/testwadt.com

In the file place the following:

# domain: testwadt.com
# public: /var/www/testwadt_com

<VirtualHost *:80>
# Admin email, Server Name (domain name), and any aliases
ServerAdmin youremail@youremailprovider
ServerName www.testwadt.com
ServerAlias testwadt.com

# Index file and Document Root (where the public files are located)
DirectoryIndex index.html index.php
DocumentRoot /var/www/testwadt_com

# Log file locations
LogLevel warn
ErrorLog /var/www/testwadt_com/log/error.log
CustomLog /var/www/testwadt_com/log/access.log combined
</VirtualHost>

Now lets create the 2nd file testwadt.net in /etc/apache2/sites-available

vi /etc/apache2/sites-available/testwadt.net

In the file place the following:

# domain: testwadt.net
# public: /var/www/testwadt_net

<VirtualHost *:80>
# Admin email, Server Name (domain name), and any aliases
ServerAdmin youremail@youremailprovider
ServerName www.testwadt.net
ServerAlias testwadt.com

# Index file and Document Root (where the public files are located)
DirectoryIndex index.html index.php
DocumentRoot /var/www/testwadt_net

# Log file locations
LogLevel warn
ErrorLog /var/www/testwadt_net/log/error.log
CustomLog /var/www/testwadt_net/log/access.log combined
</VirtualHost>

What these settings do is as follows:

ServerName listens for requests asking for a certain domain
ServerAlias defines any additional domains that should match
ServerAdmin is the contact for the site
DocumentRoot is the path to the content for that site

Now that this file is created in the /etc/apache2/sites-available/ folder we’re just about ready to start, but we need to enable it. We can do that by creating a symbolic link in /etc/apache2/sites-enabled/

This is done by calling the a2ensite command

a2ensite testwadt.com
a2ensite testwadt.net

Finally, restart the Apache server to initialize all the changes

/etc/init.d/apache2 restart

Files that configure virtual hosts should be located in the /etc/apache2/sites-available/ directory.

The files should be symbolically linked to sites-enabled/ with the a2ensite tool.

Create a Git Repository from an existing non-empty directory and Push Files to a Remote Repository

2013-05-14T12:29:00.001-07:00

From the terminal (or command line prompt in Windows) goto the non empty directory where you'd like to create a Git Repository

Run the following commands

git init

git add .

git commit -m 'Initialized my Git Repo'

Get the url of your remote repository.

For E.g in case the url is https://xyz@bitbucket.org/xyz/sample_repo.git

Run the following commands

git remote add origin https://xyz@bitbucket.org/xyz/sample_repo.git

git push -u origin master

Bookmarklets

2013-02-12T14:34:00.000-08:00

Regular bookmarks (aka favorites) are just locations to visit, like “http://gmail.com”. Bookmarklets are javascript code that the browser runs on the current page, and they’re marked by “javascript:” instead of “http://”.

Technically, a bookmarklet is unobtrusive script written in JavaScript and stored as the URL of a bookmark in a web browser or as a hyperlink on a web page.

Bookmarklets are saved and used as normal bookmarks. As such, they are simple "one-click" tools which add functionality to the browser.

For example, they can:

Modify the appearance of a web page within the browser (e.g., change font size, background color, etc.)

Extract data from a web page (e.g., hyperlinks, images, text, etc.)

Submit the current page to a curation service such as minus, scoop.it, link-shortening service such as bit.ly, or bookmarking service such as Delicious

Query a search engine or online encyclopedia with highlighted text or by a dialog box

Submit the current page to a link validation service or translation service

Set commonly chosen configuration options when the page itself provides no way to do this

"Installation" of a bookmarklet is performed by creating a new bookmark, and pasting the code into the URL destination field. Alternatively, if the bookmarklet is presented as a link, under some browsers it can be dragged and dropped onto the bookmark bar. The bookmarklet can then be run by loading the bookmark normally.

When clicking a bookmarklet, imagine the page author wrote <script>bookmarklet code here</script> — it can do almost anything. There are a few restrictions:

Restricted length: Most URLs have a limit around 2000 characters, which limits the amount of code you can run.
No spaces allowed: Some browsers choke on spaces in a URL, so yourcodelookslikethis.

SEO Tips : Page Renaming - Wordpress

2012-07-08T03:07:00.000-07:00

When changing the name of a page via wordpress, keep in mind that the earlier name page URL will not offer a 404 not found request...

This is to be avoided as this completely kills the SEO achieved on the previous URL... crawlers will keep reporting back that the page is down...

3 steps need to be done to prevent any problems:

Step 1: Report within Google Webmaster Tools that the page names have changed

Step 2: Prevent robots/crawlers from finding the problematic page:

This can be done via 2 ways:

1. Use an appropriate WordPress Plugin to ensure that when page names are changed, the Plugin will ensure that WordPress itself will offer the correct pages...

2. Write the appropriate lines in the .htaccess file to ensure that a 301 redirect is offered from the earlier specified URL to the newer URL...

Step 3: Create a custom 404 page which is user friendly and offers an alternative user navigation . The 404 page may say:

We're sorry you didnt find this page: But you can read about

A --> Here

B --> Here

C --> Here

etc

Where the links and topics should be the core topics of the business (or SEO chosen keywords)

SSL in Wamp Server

2012-07-06T01:36:00.000-07:00

SSL Encryption can be added to your Wamp Server package to make it more secure as well as to test the SSL environment before taking your application to production.

Note 1: Example given in case the folder in which apache is installed is apache2.2.6 where 2.2.6 is the version of apache installed. In case of another version being installed, say apache 2.2.22, this folder would change to apache2.2.22

Note 2: the foldername appName used below should be changed to whatever is the foldername where your application is placed which should be served to users connecting via https://

1. Create SSL Certificate and Key

Open the DOS command window and change directory to bin directory of wamp apache directory by using the DOS command

cd c:\wamp\bin\apache\apache2.2.6\bin

Now the DOS prompt should look like: C:\wamp\bin\apache\apache2.2.6\bin>

To create a server key with 1024 bits encryption, enter this command:

openssl genrsa -des3 -out server.key 1024

It’ll ask you a pass phrase, enter a passphrase of your choice which you will remember

Remove the pass phrase from the RSA private key (while keeping a backup copy of the original file). Enter these commands:

copy server.key server.key.org

openssl rsa -in server.key.org -out server.key

It’ll ask you the pass phrase you entered earlier, enter it

Create a self-signed Certificate (X509 structure) with the RSA key you just created. Enter the command:

openssl req -new -x509 -nodes -sha1 -days 365 -key server.key -out server.crt -config C:\wamp\bin\apache\apache2.2.6\conf\openssl.cnf

You'll be asked to fill in information after entering this command.

2. Copy the server.key and server.crt files

In the conf folder of apache2.2.6 folder, create two folders named as ssl.key and ssl.crt

Copy the server.key file to ssl.key folder and server.crt file to ssl.crt

3. Edit the httpd.conf file and php.ini

In httpd.conf file, remove the comment definer # at the line which says:

LoadModule ssl_module modules/mod_ssl.so

In httpd.conf, remove the comment definer # at the line which says:

Include conf/extra/httpd_ssl.conf

Then move that line after this block <IfModule ssl_module>…. </IfModule>

Open the php.ini file located in apache2.2.6/bin folder, remove the comment definer; at the line which says:

extension=php_openssl.dll

4. Edit the httpd-ssl.conf file

The httpd-ssl.conf file is located at C:\wamp\bin\apache\Apache2.2.6\conf\extra

This should be edited as follows

Find the line which says "SSLMutex …." and change it to SSLMutex default without quotes

Find the line which says: <VirtualHost _default_:443>.

Right after it, change the line which says DocumentRoot … to DocumentRoot "C:/wamp/www/appname" with quotes.

Change the line "ErrorLog…." to Errorlog C:/wamp/logs/sslerror.log without quotes

Change the line "TransferLog …." to TransferLog C:/wamp/logs/sslaccess.log without quotes

Specify the SSL crt file: Change the line "SSLCertificateFile …." to SSLCertificateFile "C:/wamp/bin/apache/apache2.2.6/conf/ssl.crt/server.crt"

Specify the SSL key file: Change the line "SSLCertificateKeyFile …." to SSLCertificateKeyFile " C:/wamp/bin/apache/apache2.2.6/conf/ssl.key/server.key"

Change the line which says <Directory "C:/Program Files/Apache Software Foundation/Apache2.2/cgi-bin"> to <Directory "C:/wamp/www/">

and add the following lines inside those <Directory … >…</Directory> tags:

Options Indexes FollowSymLinks MultiViews

AllowOverride All

Order allow,deny

allow from all

Make sure the line CustomLog "C:/wamp/logs/ssl_request.log" \ is uncommented (remove the #).

In the DOS Command window, enter httpd -t . If it displays Syntax is OK, then proceed, else you have made a syntactical error and will need to troubleshoot

Go to C:/wamp/logs and create the following 3 files

i. sslerror.log

ii. ssl_request.log

iii. sslaccess.log

5. Starting the HTTPS Server and Putting it Online

Restart the Apache server

If restart is successful, then open the browser and enter https://localhost

If you want to allow put your HTTPS secure server online then in the httpd_ssl.conf file, change the line which says "ServerName localhost:443" to "ServerName www.yourwebsitename.com:443" or "ServerName X.Y.Z.A:443" without quotes where yourwebsitename is your registered internet domain name and/or X.Y.Z.A is your WAN IP Address

The DocumentRoot you modified in Step 4 points to the correct website folder on your server.

If your server is connected to a router, setup the router to allow port 443 forwarding to your server.

If your server has a firewall enabled or behind a network firewall, set up the firewall to allow incoming port 443 connection

PHP to handle inputs copy pasted from MS Word

2012-06-18T16:38:00.002-07:00

A common problem faced is that the user wants to copy & paste their article or part of it from Microsoft Word, directly into a textarea on a page. The problem is word uses non UTF-8 characters. Once the page is submitted, PHP gets it and the characters are encoded differently and they display weirdly when displayed back via an echo.

A Commonly available solution for this is to create a function which parses the input and cleans it up either by removing the non standard characters or converting them into standard UTF-8 characters

Here is an example of one such

function fWordCharacterConverter($str)
{
$invalid = array('Š'=>'S', 'š'=>'s', 'Ð'=>'Dj', 'd'=>'dj', 'Ž'=>'Z', 'ž'=>'z',
'C'=>'C', 'c'=>'c', 'C'=>'C', 'c'=>'c', 'À'=>'A', 'Á'=>'A', 'Â'=>'A', 'Ã'=>'A',
'Ä'=>'A', 'Å'=>'A', 'Æ'=>'A', 'Ç'=>'C', 'È'=>'E', 'É'=>'E', 'Ê'=>'E', 'Ë'=>'E',
'Ì'=>'I', 'Í'=>'I', 'Î'=>'I', 'Ï'=>'I', 'Ñ'=>'N', 'Ò'=>'O', 'Ó'=>'O', 'Ô'=>'O',
'Õ'=>'O', 'Ö'=>'O', 'Ø'=>'O', 'Ù'=>'U', 'Ú'=>'U', 'Û'=>'U', 'Ü'=>'U', 'Ý'=>'Y',
'Þ'=>'B', 'ß'=>'Ss', 'à'=>'a', 'á'=>'a', 'â'=>'a', 'ã'=>'a', 'ä'=>'a', 'å'=>'a',
'æ'=>'a', 'ç'=>'c', 'è'=>'e', 'é'=>'e', 'ê'=>'e', 'ë'=>'e', 'ì'=>'i', 'í'=>'i',
'î'=>'i', 'ï'=>'i', 'ð'=>'o', 'ñ'=>'n', 'ò'=>'o', 'ó'=>'o', 'ô'=>'o', 'õ'=>'o',
'ö'=>'o', 'ø'=>'o', 'ù'=>'u', 'ú'=>'u', 'û'=>'u', 'ý'=>'y', 'ý'=>'y', 'þ'=>'b',
'ÿ'=>'y', 'R'=>'R', 'r'=>'r', "`" => "'", "´" => "'", "„" => ",", "`" => "'",
"´" => "'", "“" => "\"", "”" => "\"", "´" => "'", "â€™" => "'", "{" => "",
"~" => "", "–" => "-", "’" => "'");

$str = str_replace(array_keys($invalid), array_values($invalid), $str);

return $str;
}

Another solution which is much less known but works well is to use the php function iconv

$str= iconv('UTF-8', 'ASCII//TRANSLIT', $str);

Details from the PHP Manual:

string iconv ( string $in_charset , string $out_charset , string $str )

Performs a character set conversion on the string str from in_charset to out_charset.

Parameters

in_charset: The input charset.
out_charset: The output charset.

If you append the string //TRANSLIT to out_charset transliteration is activated. This means that when a character can't be represented in the target charset, it can be approximated through one or several similarly looking characters. If you append the string //IGNORE, characters that cannot be represented in the target charset are silently discarded. Otherwise, str is cut from the first illegal character and an E_NOTICE is generated.
str: The string to be converted.

Return Values

Returns the converted string or FALSE on failure.

array_pop and array_push in PHP

2012-05-05T00:14:00.001-07:00

array_push — Push one or more elements onto the end of array

array_push() treats array as a stack, and pushes the passed variables onto the end of array. The length of array increases by the number of variables pushed.

Has the same effect as:

<?php
$array[] = $var;
?>
repeated for each var.

array_pop — Pop the element off the end of array

array_pop() pops and returns the last value of the array, shortening the array by one element. If array is empty (or is not an array), NULL will be returned. Will additionally produce a Warning when called on a non-array.

Note: This function will reset() the array pointer of the input array after use.

Redirecting based on the URL string using PHP

2012-03-17T09:58:00.000-07:00

In many cases, one ends up hosting multiple sites on a single server, shared or VPS.

Also in many other cases a company has multiple domains and multiple page addresses to service clients and prospects from different countries, demographics and walks of life.

And the need of the hour is that one wants to send a user to a different folder on your web site, based on what domain they use? Here we will explain a simple way to do this using PHP.

For instance on my VPS, I have 2 domains pointing: one domain called sampleno1.com and the other one called sampleno2.com. Both point to the IP of the VPS.
We have an index.php file in the root of the web server on the VPS containing the following code.

<?php

if (($_SERVER['HTTP_HOST'] == “sampleno1.com”) || ($_SERVER['HTTP_HOST'] == “www.sampleno1.com”))
{
header("location: folderforsampleno1");
}

if (($_SERVER['HTTP_HOST'] == “sampleno2.com”) || ($_SERVER['HTTP_HOST'] == “www.sampleno2.com”))
{
header("location: folderforsampleno2");
}

?>

The code asks the PHP server to see what the HTTP_HOST header is. If it is sampleno1.com or www.sampleno1.com, then it redirects to the folder on the server which contains the code for the site sampleno1.

If it is sampleno2.com or www.sampleno2.com, then it redirects to the folder on the server which contains the code for the site sampleno2

Find a File containing a specific text string in Ubuntu

2012-03-03T00:16:00.000-08:00

Find a File containing a specific text string in Ubuntu can be done using the grep command.

The format is

grep “text string to search” directory-path

Some Examples

Simple String Search in a directory:
Search for a string called "star wars" in all text files located in /home/movies/*.txt directory, use

$ grep "star wars" /home/movies/*.txt

Search for a string in all files in all contained folders

For this, you can search for a text string all files under each directory, recursively with -r option:

$ grep -r "star wars" /home/movies/

Determine file size with du

2012-02-06T13:55:00.000-08:00

The du command ( disk usage ) gather and summarize about how much your disk space being used by your file and the disk space being use by directory in the Linux system The du command can be use to find the size of file and the size of directory in Linux system.

du takes a single argument, specifying a pathname for du to work; if it is not specified, the current directory is used. The SUS mandates for du the following options:

-a, display an entry for each file (and not directory) contained in the current directory

-H, calculate disk usage for link references specified on the command line

-k, show sizes as multiples of 1024 bytes, not 512-byte

-L, calculate disk usage for link references anywhere

-s, report only the sum of the usage in the current directory, not for each file

-x, only traverse files and directories on the device on which the pathname argument is specified.

du is flexible and offers a variety of options. For example, it allows you to determine the size of the current directory and all subdirectories:

$ du -sh

Using du by itself displays the size of every subdirectory under the current directory--it summarizes and reports the data in human-readable format, such as 402 MB instead of 411012 bytes. You can also see the size of every file in every subdirectory by incorporating the "-a" option:

$ du -ah

In addition, you can use du in combination with grep to find a particular file size. If you're searching in a directory and suspect a file is growing extremely large, reduce the output of du to all files and directories 1 GB in size or larger with this command:

$ du -ah|grep -e '[0-9]G'

Examples

Sum of directories in kilobytes:

 $ du -sk *
 152304  directoryOne
 1856548 directoryTwo

Sum of directories in human-readable format (Byte, Kilobyte, Megabyte, Gigabyte, Terabyte and Petabyte):

 $ du -sh *
 149M directoryOne
 1.8G directoryTwo

disk usage of all subdirectories and files including hidden files within the current directory (sorted by filesize) :

 $ du -sk .[!.]* *| sort -n

disk usage of all subdirectories and files including hidden files within the current directory (sorted by reverse filesize) :

 $ du -sk .[!.]* *| sort -nr

The weight of directories:

 $ du -d 1 -c -h

More information on du command:

# info du

# man du

# du --help

node-static for Serving Static Files with Node.js

2012-02-02T23:24:00.000-08:00

node-static can be installed via npm with the following command:

npm install node-static

To use it: include the module in your script via the require function, create a server, pass it your preferred options, and tell it to serve files:

var static = require('node-static'),
  http = require('http'),
  util = require('util');
var webroot = './public',
  port = 8181;
var file = new(static.Server)(webroot, {
  cache: 900,
  headers: { 'X-Powered-By': 'node-static' }
});
http.createServer(function(req, res) {
  req.addListener('end', function() {
    file.serve(req, res, function(err, result) {
      if (err) {
        console.error('Error serving %s - %s', req.url, err.message);
        if (err.status === 404 || err.status === 500) {
          file.serveFile(util.format('/%d.html', err.status), err.status, {}, req, res);
        } else {
          res.writeHead(err.status, err.headers);
          res.end();
        }
      } else {
        console.log('%s - %s', req.url, res.message);
      }
    });
  });
}).listen(port);
console.log('node-static running at http://localhost:%d', port);

Here, when we create a new instance of a node-static server, we pass it:

the directory we want it to serve files from by way of the `webroot` variable (defaults to serving files from the current directory unless you tell it otherwise)
a cache value of 900, so each file served will be cached for 15 minutes (default value for cache is 3600, meaning files are cached for 1 hour)
a custom ‘X-Powered-By’ header (I’ve used X-Powered-By solely as an example – you may, or may not, want to disclose the software you’re server is running)

We then use the http module’s createServer function, and add an event handler for the request’s end event where we use our instance of node-static to serve the files.

When we call file.serve, we pass it an optional callback function that let’s us customise how we handle any errors:

we check err.status, and serve either 404.html or 500.html accordingly
if there’s an error and the status code is something other than 404 or 500, we send the status code and the headers back to the client explicitly – when you pass a callback function to file.serve and there is an error, node-static will not respond to the client by itself.

Working with MySQL Events

2012-01-17T13:14:00.000-08:00

MySQL events were added in MySQL 5.1.6 and offer an alternative to scheduled tasks and cron jobs. Events can be used to create backups, delete stale records, aggregate data for reports, and so on. Unlike standard triggers which execute given a certain condition, an event is an object that is triggered by the passage of time and is sometimes referred to as a temporal trigger. You can schedule events to run either once or at a recurring interval when you know your server traffic will be low.

In this article I’ll explain what you need to know to get started using events: starting the event scheduler, adding events to run once or multiple times, viewing existing events, and altering events. I’ll also share with how you might use MySQL events using scheduled blog posts as a practical example.

Starting the Event Scheduler

The MySQL event scheduler is a process that runs in the background and constantly looks for events to execute. Before you can create or schedule an event, you need to first turn on the scheduler, which is done by issuing the following command:

mysql> SET GLOBAL event_scheduler = ON;

Likewise, to turn all events off you would use:

mysql> SET GLOBAL event_scheduler = OFF;

Once the event scheduler is started, you can view its status in MySQL’s process list.

mysql> SHOW PROCESSLIST\G
...
     Id: 79
   User: event_scheduler
   Host: localhost
     db: NULL
Command: Daemon
   Time: 12
  State: Waiting on empty queue
   Info: NULL

Working with Events

It’s important to note that when an event is created it can only perform actions for which the MySQL user that created the event has privileges to perform. Some additional restrictions include:

Event names are restricted to a length of 64 characters.
As of MySQL 5.1.8, event names are not case-sensitive; each event name should be unique regardless of case.
Events cannot be created, altered, or dropped by another event.

You cannot reference a stored function or user-defined function when setting the event schedule.

Creating Events

The following example creates an event:

01DELIMITER |
02 
03CREATE EVENT myevent
04    ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
05    DO
06      BEGIN
07        UPDATE mytable SET mycol = mycol + 1;
08      END |
09 
10DELIMITER ;

This event will run once, one hour from the time it was created. The BEGIN and END statements surround one or multiple queries which will be executed at the specified time. Because the semicolon is needed to terminate the UPDATE statement, you’ll need to switch delimiters before you issue the CREATE EVENT statement and then switch back afterwards if you’re working through a client.

You can view a list of all existing events with SHOW EVENTS.

mysql> SHOW EVENTS\G
********************** 1. row **********************
                  Db: mysql
                Name: myevent
             Definer: dbuser@localhost
           Time zone: SYSTEM
                Type: ONE TIME
          Execute At: 2011-10-26 20:24:19
      Interval Value: NULL
      Interval Field: NULL
              Starts: NULL
                Ends: NULL
              Status: ENABLED
          Originator: 0
character_set_client: utf8
collation_connection: utf8_general_ci

After an event has expired it will be automatically deleted unless you explicitly stated otherwise with an ON COMPLETION clause, for example:

1CREATE EVENT myevent
2    ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
3    ON COMPLETION PRESERVE
4    DO
5      BEGIN
6        UPDATE mytable SET mycol = mycol + 1;
7      END |

In this example, even though the event has expired it will still be retained in the database which will allow you to alter and run it again later, or perhaps you’d just like to keep it for reference.

To permanently delete an event yourself, you can use DROP EVENT:

1DROP EVENT myevent;

To specify a recurring event, you would use the EVERY clause:

1CREATE EVENT myevent
2    ON SCHEDULE EVERY 1 HOUR
3    DO
4      BEGIN
5        UPDATE mytable SET mycol = mycol + 1;
6      END |

And rather than having an event that just runs once or forever, you can also schedule a reoccurring event that is valid only within a specific time period, using START and END clauses:

1CREATE EVENT myevent
2    ON SCHEDULE EVERY 1 HOUR
3    STARTS CURRENT_TIMESTAMP + INTERVAL 1 DAY
4    ENDS CURRENT_TIMESTAMP + INTERVAL 1 YEAR
5    DO
6      BEGIN
7        UPDATE mytable SET mycol = mycol + 1;
8      END |

In this example, the reoccurring event would start tomorrow and continue to run every hour for a full year.

With regard to timing, the interval specified can be YEAR, MONTH, WEEK, DAY, HOUR, MINUTE, orSECOND. Keep in mind that keywords are given as singular forms; writing something like INTERVAL 5 MINUTE may seem awkward to you, but it is perfectly correct to MySQL.

Updating Events

If you want to change an existing event’s behavior rather than deleting it and recreating it, you can use ALTER EVENT. For example, to change the schedule of the previous event to run every month, starting at some date in the future at 1 o’clock in the morning, you would use the following:

1ALTER EVENT myevent
2    ON SCHEDULE EVERY 1 MONTH
3    STARTS '2011-12-01 01:00:00' |

To update the event with a different set of queries, you would use:

1ALTER EVENT myevent
2    DO
3      BEGIN
4        INSERT INTO mystats (total)
5          SELECT COUNT(*) FROM sessions;
6        TRUNCATE sessions;
7      END |

To rename an event, you would specify a RENAME clause:

1ALTER EVENT myevent
2    RENAME TO yourevent;

Blog Post Scheduling

So that I can show you a practical example, let’s say you have a blog and you want the option to schedule posts to be published at some time in the future. One way to achieve this is to add a timestamp and published flag to the database records. A cron script would execute once every minute to check the timestamps and flip the flag for any posts that should be published. But this doesn’t seem very efficient. Another way to achieve this is by using MySQL events that will fire when you want publish the post.

Your blog entry form might have a checkbox that, when checked, indicates this is a scheduled post. Additionally, the form would have input fields for you to enter the date and time of when the post should be published. The receiving script would be responsible for adding the blog entry to the database and managing the events to schedule it if it’s not an immediate post. The relevant code looks like the following:

01<?php
02// establish database connection and filter incoming data
03// ...
04 
05// insert blog post with pending status, get id assigned to post
06$query = "INSERT INTO blog_posts (id, title, post_text, status)
07    VALUES (NULL, :title, :postText, 'pending')";
08$stm = $db->prepare($query);
09$stm->execute(array(":title" => $title, ":postText" => $text));
10$id = $db->lastInsertId();
11 
12// is this a future post?
13if (isset($_POST["schedule"], $_POST["time"])) {
14    $scheduleDate = strtotime($_POST["time"]);
15 
16    $query = "CREATE EVENT publish_:id
17    ON SCHEDULE AT FROM_UNIXTIME(:scheduleDate)
18    DO
19      BEGIN
20        UPDATE blog_posts SET status = 'published' WHERE id = :id;
21      END";
22    $stm = $db->prepare($query);
23    $stm->execute(array(":id" => $id, ":scheduleDate" =>$scheduleDate));
24}
25// this is not a future post, publish now
26else {
27    $query = "UPDATE blog_posts SET status = 'published' WHERE id = :id";
28    $stm = $db->prepare($query);
29    $stm->execute(array(":id" => $id));
30}

When the post is stored in the database it is saved with a pending status. This gives you the chance to schedule the event if it’s a scheduled post, otherwise the status can be immediately updated to published.

If you were to edit the post at a later time, you can delete the event with DROP EVENT IF EXISTSand re-add it with the new scheduled time.

Attach a handler to an event for the elements in jQuery

2012-01-07T15:47:00.000-08:00

As of jQuery 1.7, the .on() method is the preferred method for attaching event handlers to a document. For earlier versions, the .bind() method is used for attaching an event handler directly to elements.

Handlers are attached to the currently selected elements in the jQuery object, so those elements must exist at the point the call to .bind() occurs.

.bind( eventType [, eventData], handler(eventObject) )
eventTypeA string containing one or more DOM event types, such as "click" or "submit," or custom event names.
eventDataA map of data that will be passed to the event handler.
handler(eventObject)A function to execute each time the event is triggered.
version added: 1.4.3.bind( eventType [, eventData], preventBubble )
eventTypeA string containing one or more DOM event types, such as "click" or "submit," or custom event names.
eventDataA map of data that will be passed to the event handler.
preventBubbleSetting the third argument to false will attach a function that prevents the default action from occurring and stops the event from bubbling. The default is true.
version added: 1.4.bind( events )
eventsA map of one or more DOM event types and functions to execute for them.

The .on() method attaches event handlers to the currently selected set of elements in the jQuery object.
- .on( events [, selector] [, data], handler(eventObject) )
  eventsOne or more space-separated event types and optional namespaces, such as "click" or "keydown.myPlugin".
  selectorA selector string to filter the descendants of the selected elements that trigger the event. If the selector is null or omitted, the event is always triggered when it reaches the selected element.
  dataData to be passed to the handler in event.data when an event is triggered.
  handler(eventObject)A function to execute when the event is triggered. The valuefalse is also allowed as a shorthand for a function that simply does return false.
- version added: 1.7.on( events-map [, selector] [, data] )
  events-mapA map in which the string keys represent one or more space-separated event types and optional namespaces, and the values represent a handler function to be called for the event(s).
  selectorA selector string to filter the descendants of the selected elements that will call the handler. If the selector is null or omitted, the handler is always called when it reaches the selected element.
  dataData to be passed to the handler in event.data when an event occurs.

Year Data Type in MySQL

2012-01-07T14:57:00.000-08:00

The YEAR type is a one-byte type used for representing years. It can be declared as YEAR(2) or YEAR(4) to specify a display width of two or four characters. The default is four characters if no width is given.

For four-digit format, MySQL displays YEAR values in YYYY format, with a range of 1901 to 2155, or 0000. For two-digit format, MySQL displays only the last two (least significant) digits; for example, 70 (1970 or 2070) or 69(2069).

You can specify input YEAR values in a variety of formats:

As a four-digit string in the range '1901' to '2155'.
As a four-digit number in the range 1901 to 2155.
As a two-digit string in the range '00' to '99'. Values in the ranges '00' to '69' and '70' to '99' are converted to YEAR values in the ranges 2000 to 2069 and 1970 to 1999.
As a two-digit number in the range 1 to 99. Values in the ranges 1 to 69 and 70 to 99 are converted to YEARvalues in the ranges 2001 to 2069 and 1970 to 1999. Note that the range for two-digit numbers is slightly different from the range for two-digit strings, because you cannot specify zero directly as a number and have it be interpreted as 2000. You must specify it as a string '0' or '00' or it is interpreted as 0000.
As the result of a function that returns a value that is acceptable in a YEAR context, such as NOW().

Illegal YEAR values are converted to 0000.

MySQL Data Type Default Values When Creating Tables

2012-01-07T13:46:00.000-08:00

The DEFAULT value clause in a data type specification indicates a default value for a column. With one exception, the default value must be a constant; it cannot be a function or an expression. This means, for example, that you cannot set the default for a date column to be the value of a function such as NOW() or CURRENT_DATE. The exception is that you can specify CURRENT_TIMESTAMP as the default for a TIMESTAMP column.

As of MySQL 5.0.2, if a column definition includes no explicit DEFAULT value, MySQL determines the default value as follows:

If the column can take NULL as a value, the column is defined with an explicit DEFAULT NULL clause. This is the same as before 5.0.2.

If the column cannot take NULL as the value, MySQL defines the column with no explicit DEFAULT clause. Exception: If the column is defined as part of a PRIMARY KEY but not explicitly as NOT NULL, MySQL creates it as aNOT NULL column (because PRIMARY KEY columns must be NOT NULL), but also assigns it a DEFAULT clause using the implicit default value. To prevent this, include an explicit NOT NULL in the definition of any PRIMARY KEYcolumn.

For data entry for a NOT NULL column that has no explicit DEFAULT clause, if an INSERT or REPLACE statement includes no value for the column, or an UPDATE statement sets the column to NULL, MySQL handles the column according to the SQL mode in effect at the time:

If strict SQL mode is not enabled, MySQL sets the column to the implicit default value for the column data type.
If strict mode is enabled, an error occurs for transactional tables and the statement is rolled back. For nontransactional tables, an error occurs, but if this happens for the second or subsequent row of a multiple-row statement, the preceding rows will have been inserted.

Suppose that a table t is defined as follows:

CREATE TABLE t (i INT NOT NULL);

In this case, i has no explicit default, so in strict mode each of the following statements produce an error and no row is inserted. When not using strict mode, only the third statement produces an error; the implicit default is inserted for the first two statements, but the third fails because DEFAULT(i) cannot produce a value:

INSERT INTO t VALUES();
INSERT INTO t VALUES(DEFAULT);
INSERT INTO t VALUES(DEFAULT(i));

See Section 5.1.6, “Server SQL Modes”.

For a given table, you can use the SHOW CREATE TABLE statement to see which columns have an explicitDEFAULT clause.

SERIAL DEFAULT VALUE in the definition of an integer column is an alias for NOT NULL AUTO_INCREMENT UNIQUE.

Foreign Keys in MySQL - InnoDB supports foreign key constraints

2012-01-07T12:44:00.000-08:00

Here is a simple example that relates parent and child tables through a single-column foreign key:

CREATE TABLE parent (id INT NOT NULL,
                     PRIMARY KEY (id)
) ENGINE=INNODB;


CREATE TABLE child (id INT, parent_id INT,
                    INDEX par_ind (parent_id),
                    FOREIGN KEY (parent_id) REFERENCES parent(id)
                      ON DELETE CASCADE
) ENGINE=INNODB;

A more complex example in which a product_order table has foreign keys for two other tables. One foreign key references a two-column index in the product table. The other references a single-column index in the customertable:

CREATE TABLE product (category INT NOT NULL, id INT NOT NULL,
                      price DECIMAL,
                      PRIMARY KEY(category, id)) ENGINE=INNODB;

CREATE TABLE customer (id INT NOT NULL,
                       PRIMARY KEY (id)) ENGINE=INNODB;

CREATE TABLE product_order (no INT NOT NULL AUTO_INCREMENT,
                            product_category INT NOT NULL,
                            product_id INT NOT NULL,
                            customer_id INT NOT NULL,
                            PRIMARY KEY(no),
                            INDEX (product_category, product_id),
                            FOREIGN KEY (product_category, product_id)
                              REFERENCES product(category, id)
                              ON UPDATE CASCADE ON DELETE RESTRICT,
                            INDEX (customer_id),
                            FOREIGN KEY (customer_id)
                              REFERENCES customer(id)) ENGINE=INNODB;

InnoDB enables you to add a new foreign key constraint to a table by using ALTER TABLE:

ALTER TABLE tbl_name
    ADD [CONSTRAINT [symbol]] FOREIGN KEY
    [index_name] (index_col_name, ...)
    REFERENCES tbl_name (index_col_name,...)
    [ON DELETE reference_option]
    [ON UPDATE reference_option]

The foreign key can be self referential (referring to the same table). When you add a foreign key constraint to a table using ALTER TABLE, remember to create the required indexes first.

Foreign Keys and ALTER TABLE

InnoDB supports the use of ALTER TABLE to drop foreign keys:

ALTER TABLE tbl_name DROP FOREIGN KEY fk_symbol;

Identify Foreign Key Creation Failure

If MySQL reports an error number 1005 from a CREATE TABLE statement, and the error message refers to error 150, table creation failed because a foreign key constraint was not correctly formed.