Q&A with Ben Hoelting: Top Tips on JavaScript Patterns for the C# Developer

From variables to inheritances to what JavaScript patterns you really need to know, C# MVP Ben Hoelting offers his top tips for C# coders looking to use JavaScript to build complex client-side Web apps.

When picking up JavaScript design patterns, which are crucial for complex client-side Web applications, there's a few areas that every C# developer finds issues with (or just using JavaScript in general) -- like the lack of simple keywords or differences in inheritances. Ben Hoelting, C# MVP and speaker at the upcoming Visual Studio Live! Boston conference, offers his top tips below for which patterns to focus on and the differences you need to understand to quickly transition (plus what not to do).

What are the top 3 differences between JavaScript and C# that are the most challenging in general for C# developers?
By far the biggest difference between JavaScript and C# is that JavaScript is a dynamically typed language and C# is a static or strongly typed language. This means that you can define a variable and assign a string to it and later in the code assign a number to it without causing an error. If you do that in C# your code will not compile. That is what we love about C#, the compiler lets us know if we do something that is a bad practice.

Another key difference is how scoping works. Most C# developers struggle with this when it comes to the "this" keyword. "This" is not always the object or function you are in. It is determined by how the function or object is called. "This" throws most people for a loop. Pun intended.

There are other differences but a key thing to understand is that as JavaScript's standards are evolving many things are improving. Some of these differences are going away as browsers catch up with the new ECMAScript standards.

How does inheritance work differently in JavaScript?
Inheritance is different in JavaScript than it is in any other languages. Since JavaScript is a dynamic language, it allows objects to be changed at run time. We can use a concept called Prototypes to add the behavior of one object to another. That is how JavaScript inheritance works. We add the behaviors of the base class to the concrete class at run time.

As you point out in your Visual Studio Live! Boston session on this topic, Design Patterns are key to using JavaScript effectively for larger applications -- what are your top tips for C# developers when it comes to JavaScript Design Patterns?
One of the most important patterns to understand in JavaScript is the Module pattern. This pattern is used to encapsulate functionality in JavaScript. In essence, they can be used to create something that is equivalent to a class in C#. The Module pattern uses the scoping functionality in JavaScript to keep certain variables and/or functions private to the Module. It can then "reveal" the variables and functions it allows the consumers of the module to use.

"Another pattern that a JavaScript developer must become very familiar with is the idea of a Promise. A Promise is the way JavaScript handles async programming."

Ben Hoelting, C# MVP, Senior Technologist, Aspenware

Another pattern that a JavaScript developer must become very familiar with is the idea of a Promise. A Promise is the way JavaScript handles async programming. So, most of the popular frameworks return a Promise when potentially long-running/thread-blocking functions are called. This is a Promise to call back to the consumer when the long-running process is complete. It is similar for the Async pattern in C#, but implemented differently.

Obviously, there are many other patterns to learn but these two will help you get started with JavaScript programming.

What is the number one thing that you recommend C# developers to NOT do when they're picking up JavaScript Patterns?
Some of the biggest issues with JavaScript programming do not have anything to do with patterns or coding. The biggest issues come down to building, packaging, deploying and debugging your code. In JavaScript development, the browser is the compiler and the runtime environment. So, figuring out how to develop and debug your code quickly to be the most productive is key.

What else should developers know about this topic?
I think any C# developer that is planning to build a complex client-side application like a Single Page Application (SPA) should use TypeScript. TypeScript adds syntax to JavaScript that allows developers to compile their application as they are coding it. What I mean by this is that Visual Studio or VS Code can give you red squiggles as you code. So, you don't have to wait to run it in a browser to see any JavaScript errors. This gives early feedback to developers and helps to enforce best practices.

Learn more about this and other great topics and Visual Studio Live! Boston in June 2018.

About the Author

Becky Nagel is vice president of AI for 1105 Media, where she specializes in training internal and external customers on maximizing their business potential via a wide variety of generative AI technologies as well as developing cutting-edge AI content and events. She's the author of "ChatGPT Prompt 101 Guide for Business Uses," regularly leads research studies on generative AI business usage, and serves as the director of AI Boardroom, a new resource for C-level executives looking to excel in the AI era. Prior to her current position she was a technical leader for 1105 Media's Web, advertising and production teams as well as editorial director for a suite of enterprise technology publications, including serving as founding editor of She has 20 years of enterprise technology journalism experience, and regularly speaks and writes about generative AI, AI, edge computing and other cutting-edge technologies. She can be reached at [email protected].

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