C#
C# 14 Extension Members Explained
Extension members let you add properties, static members and operators to types you do not own, not just methods. The new extension…
All guides
Every guide on the site, newest first. Explanations, projects and fixes written in plain English.
JavaScript
The JavaScript Double Exclamation Mark, Explained
What the double exclamation mark actually does in JavaScript, why it is not an operator, when it is genuinely useful, and when…
JavaScript
TypeScript vs JavaScript: Which Should a Beginner Learn?
TypeScript is JavaScript with types checked before the code runs. What that buys, what it costs, and a clear answer on learning…
C#
C# Generics
Generic classes, methods and constraints in C#, why the generic List beats ArrayList, and the variance keywords in and out explained plainly.
JavaScript
Introduction to ES6 and Beyond
The JavaScript features added since 2015 that changed how the language is written: let and const, arrow functions, destructuring, modules, async/await and…
JavaScript
TypeScript 7: What the Native Compiler Changes for You
TypeScript 7 replaced the JavaScript-based compiler with a port written in Go. Builds and editor checks are several times faster. What changed,…
Python
Choosing the Right Python Version for Windows 10
Which Python version to install on Windows 10, where to get it, why the Microsoft Store version causes problems, and how to…
JavaScript
Fixing “error is of type unknown” in TypeScript catch Blocks
Since TypeScript 4.4, a caught value is unknown, not any. Why that is correct, the three ways to handle it, and a…
PHP
PHP Performance Optimization
Where PHP applications actually spend their time, how to measure before you optimise, and the fixes that matter: OPcache, N+1 queries, indexes…
JavaScript
Fixing “TypeError: x is not a constructor”
You used new on something that cannot be constructed: an arrow function, an object, an undefined import, or a module instead of…
C#
C# Testing
Writing unit tests in C# with xUnit: arrange-act-assert, parameterised tests, mocking dependencies, and what is actually worth testing.
Python
Fixing “NameError: name is not defined” in Python
Python cannot find a name at the moment you used it. A typo, a variable used before it was assigned, a function…
Keep going — pick your next guide
The fastest way to improve is to read one guide, then build the thing it describes. Start with the basics, or jump straight to a project.