JavaScript/TypeScript Testing a function specified in callback that cannot be triggered in test
Don't you have a good idea to write a test of the logic specified in a callback function? Isn't it possible to control t...
JavaScript/TypeScript 
Dart and Flutter Dart – how to assign int/String values to enum
Dart supports only the simplest case on enum and its index always starts from 0. However, we often want to assign values...
Dart and Flutter Dart – Understanding Class Initialization Order
I wrote simple code to understand class initialization order. Dart offers late keyword to check null at runtime instead ...
Dart and Flutter Dart compiler doesn’t recognize if a variable is non-null value
Dart compiler doesn't recognize even though null check logic exists before using the variable. It took me a while to und...
JavaScript/TypeScript How to Restrict Possible String Arguments
I want to limit the possible string arguments. How can I do it? This article is for you. I will show 4 ways to do it.The...
JavaScript/TypeScript Define array with multiple types in TypeScript
Union type or tuple is useful to define multiple types in an array. It shows how to define it and use cases. However, if there are multiple types in an array, it's harder to handle the difference. Using an interface is often a better choice.
Other techs How to write outer join more than 3 tables
How can we write outer join to merge multiple tables? Do you need subquery in the query? This article shows you the solution.
Tips How to backup photos automatically
This article shows how to automatically copy files that don't exist in the destination directory. I often copy files fro...
Other techs Establish SQL Server in Docker container
I tried to establish SQL Server in Docker because I wanted to learn SQL again.Create a Dockerfile and runIt's possible t...
Tips Difficulties of personal evaluation for programmer
I have an interview session twice a year for my personal evaluation. I have to set goals at start of the year and have t...