The meaning of life is to explore the world

Error class in JS has the message property.
We should try to throw Error object instead of other random stuff like boolean, string etc.
This includes errors thrown from Promise.reject()
E.g. In the codes below, test(f1) works while test(f2) does not.

JS has no overloading.
Instead, the later function overwrites the earlier ones.
E.g. In the codes below, the output will be no param.

There are some reasons we may want to convert a class component to a functional component.
E.g. Hooks are only available in functional components like const queryString = useLocation().search;
This can be quite useful in React Router.

Usually each web API request sends with a cookie, and the response has a new cookie that is used by next request. However if we use document.cookie to get the cookie it may not be accurate if there’re multiple requests and responses.

There are some key differences between <button/> and <input type=”button” />:

To update my earlier blog post PUBLIC_URL in React is not dynamic , I have found a solution to it.

1. Cache of the Outlook add-in needs to be cleared before any update of it can apply
   • Reinstall the add-in
   • for /d %d in ("%LOCALAPPDATA%\Microsoft\Office\16.0\Wef\*") do @rmdir /s /q "%d"
   • del /s /f /q /a:h %LOCALAPPDATA%\Packages\Microsoft.Win32WebViewHost_cw5n1h2txyewy\AC\#!123\INetCache\*
   • rmdir /s /q %userprofile%\AppData\Local\Microsoft\Outlook\HubAppFileCache
     References:
     MS docs to clear cache
     Some ways to clear cache

E.g.1:

SELECT 
	TO_CHAR(DATE_TRUNC('month', TO_TIMESTAMP(epoch_sec)), 'MM/YY') AS month,
	COUNT(CASE WHEN my_val = 3 THEN 1 END) AS matched,
	COUNT(*) AS total
FROM my_tab
GROUP BY month
ORDER BY month

Error:

psql: error: connection to server on socket "/var/run/postgresql/.s.PGSQL.5432" failed: FATAL:  sorry, too many clients already

Error:

    #8 [4/5] RUN npm install
    #8 18.80 npm ERR! code EMFILE
    #8 18.80 npm ERR! syscall open
    #8 18.80 npm ERR! path /root/.npm/_cacache/index-v5/a0/7a/7e48bcbef3e333c0cda8208f4902ea385bb700f4d8c414525a120c4bba14
    #8 18.80 npm ERR! errno -24
    #8 18.80 npm ERR! EMFILE: too many open files, open '/root/.npm/_cacache/index-v5/a0/7a/7e48bcbef3e333c0cda8208f4902ea385bb700f4d8c414525a120c4bba14'
    #8 18.85 
    #8 18.85 npm ERR! A complete log of this run can be found in: /root/.npm/_logs/2024-03-24T20_54_30_709Z-debug-0.log
    #8 ERROR: process "/bin/sh -c npm install" did not complete successfully: exit code: 232

There’s an industry wide change of where to store the private key of a code signing certificate. Most if not all CAs have adopted and announced this change, e.g. DigiCert: https://knowledge.digicert.com/generalinformation/new-private-key-storage-requirement-for-standard-code-signing-certificates-november-2022.html

Things to be changed as migrating from MySql to PostgreSQL

Symptom
PUBLIC_URL is a system variable defined in file .env and used by Create React App.
Once we run npm run build, this is the base URL as a static string.
It cannot be dynamically set in a configuration file at run time.
As a result, if two builds are using different PUBLIC_URL then they have to be built separately, which is bad for containerization.

solution
So far I have found no solution

Upgrading MongoDB driver in .NET project causing dependent assembly error

How to route network traffic from same port to different containers

Some Azure pipeline pitfalls to be aware of

CSS <td> max-height is not working for large text

Below are some hints to use Azure pipeline

How to serialize enums to ints instead of strings with Gson?
(Below answer is from chatGPT)
By default, the Gson library serializes enums into strings. However, if you want to serialize enums into integers instead of strings, you can create a custom Gson serializer/deserializer for your enum class. Here’s an example of how you can achieve this:

What is the output of below? 1? 3? 5? 6?\

int? x = null;
int val = 1 + x ?? 2 + 3;
Console.WriteLine(val);

some ways to share data among React components
1.static data of a class

Problem
In the example below, GetData_1() throws null pointer exception whereas GetData_2() returns a value. Why?

React state life cycle
See the link from offical webiste:
https://projects.wojtekmaj.pl/react-lifecycle-methods-diagram/

setState() may have delayed effect
This is because it is asynchronous method.
Reading this.state may get the wrong state.

You may want to use npx create-react-app my-app-name as a starting point.

But there still can be issues like below.

Intellij intellisense does not recognize classes or methods. How to fix it?

1. Find cmd parameter needs to be double quoted

Summary:
UnityContainer is one of the libraries to implement dependency injection in C#.

Problem:
GitHub Dependabot alerts on old libraries, pointing out security vulnerabilities.

Problem:
grep command in Linux doesn’t support UTF-16.

Problem:

// Create an Image class with two properties, Width and Height
// Whenever Width is updated, Height should be updated in proportion
// Tips: avoid below 2 traps
// 1. Updating Width and Height triggers an infinite dead loop
// 2. The dependent update triggered incorrectly by the object initialization or copy

Please refer to the link below:
https://saebamini.com/common-async-and-await-misconceptions/

Is it possible to crash in a class before its constructor runs?
Yes.
One possibility is it cannot load the libraries it’s referencing.
E.g.

If the actual log4net.dll is not under version 1.2.13.0, then the crash will happen.

Some tips for beginners developing Android apps using Kotlin in Android Studio

1. Useful references:
   • Google documentation
     https://developer.android.com/topic/architecture

Error message:

17:12:28.224 ERROR [com.Company.program.boot.programApplicationLauncher.main()] o.s.boot.SpringApplication - Application startup failed
java.lang.IllegalStateException: Cannot load configuration class: com.Company.program.boot.config.ApplicationConfiguration
 at org.springframework.context.annotation.ConfigurationClassPostProcessor.enhanceConfigurationClasses(ConfigurationClassPostProcessor.java:395) ~[spring-context-4.1.6.RELEASE.jar:4.1.6.RELEASE]
 ......
 at java.base/java.lang.Thread.run(Thread.java:833) ~[na:na]
Caused by: java.lang.ExceptionInInitializerError: null
 at org.springframework.cglib.core.KeyFactory$Generator.generateClass(KeyFactory.java:166) ~[spring-core-4.1.6.RELEASE.jar:4.1.6.RELEASE]
 ......
 ... 17 common frames omitted
Caused by: java.lang.reflect.InaccessibleObjectException: Unable to make protected final java.lang.Class java.lang.ClassLoader.defineClass(java.lang.String,byte[],int,int,java.security.ProtectionDomain) throws java.lang.ClassFormatError accessible: module java.base does not "opens java.lang" to unnamed module @43905a1d
 at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:354) ~[na:na]
 ......
 ... 28 common frames omitted

Triple back ticks ``` used to work but no longer does now.

Test your knowledge with below questions:

Some tips on how to do outer joins in LINQ

Some tips of Git branching

Some practical tips against traps in T-SQL

LINQ is better than SQL in some ways. https://www.linqpad.net/WhyLINQBeatsSQL.aspx

Below is an example of using IEnumerable and yield.

Early this month I got the Microsoft Azure Administrator Associate Certificate.
Badge as below.

An example of SQL table joining special skill

Microsoft Ignite Azure Admin Challenge

Ansible variable precedence
(Bottom has the highest precedence)

Ansible tips

Demo page:
Link to demo

Problem:
After chmod, the permissions got lost due to being overwritten by Windows

1. Update apt

sudo apt-get update
......
Fetched 7978 kB in 1min 41s (79.3 kB/s)
Reading package lists... Done

1. Docker mistakes some files for folders, and folders for files.

1. Ubuntu Docker container doesn’t have Chinese by default.
   Solution:
   • Option 1: install Chinese manually
     ```bash #Check locale locale -a #Check installed packages dpkg -l | less

Commands

1. Failed to upgrade to 2.3.0.5
   ```bat Attempted to perform an unauthorized operation. at Microsoft.Win32.RegistryKey.Win32Error(Int32 errorCode, String str) at Microsoft.Win32.RegistryKey.SetValue(String name, Object value, RegistryValueKind valueKind) at CommunityInstaller.AutoStartAction.DoAsync(CancellationToken cancelToken) at CommunityInstaller.InstallWorkflow.d__34.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at CommunityInstaller.InstallWorkflow.d__29.MoveNext()

1. GitHub may have connection error like this:

   git push -u origin master
   fatal: unable to access 'https://github.com/jasonmccb/myWSLSync.git/': Could not resolve host: github.com
   

Please reference the bash code example of syncing folders from one drive to another under WSL here:
https://github.com/jasonmccb/myWSLSync.git

1. USB disk needs to be mounted MANUALLY from time to time

   sudo mkdir /mnt/e
   sudo mount -t drvfs E: /mnt/e
   sudo umount /mnt/e
   

1. rsync Linux man page:
   https://linux.die.net/man/1/rsync

A link to CMake set up:

https://blog.csdn.net/Bruce_0712/article/details/53574170

1. Please see the table below.

1. AWS cheat sheet is a good reference for basic AWS concepts. It also has a site search function.
   https://digitalcloud.training/certification-training/aws-certified-cloud-practitioner/

Tips

1. Use git help <verb> to learn the Git commands.

1. Why Singleton class needs to be sealed?
   https://dotnettutorials.net/lesson/singleton-class-sealed/
   In short, internal derived class will be able to create instances.

How to install Algolia and push content?
https://community.algolia.com/jekyll-algolia/getting-started.html

1. How to run Ruby program:
   ruby test.rb
   or
   irb

In the Notepad++ menubar click Edit -> EOL Conversion to format carriage return in entire file.
A link to guide

Summary:

Windows 10 does support Linux subsystem.(A link to guide)
Here’s a summary of how to install Ubuntu on Win 10.

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Company holiday

Public holiday

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Comany holiday.

Comany holiday.

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Comany holiday.

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Comany holiday.

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Public holiday.

Public holiday. Went tramping at Orongorongo Track, having a good time.

Public holiday. Happy 2020.

Annual leave. Happy new year.

What have been done:

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Public holiday. Merry Christmas.

Public holiday. Merry Christmas.

Public holiday. Merry Christmas.

What have been done:

Annual leave.

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Annual leave.

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Nothing has been today as I am on sick leave.

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Day 1 is about setting up the environment and the tools, and also the introduction of the beer web architecture. What have been done: