The Day I Banned JavaScript from Production: Why TypeScript is Non-Negotiable.

"Undefined is not a function."
​If you are a web developer, that sentence probably raised your blood pressure. It is the most common error in JavaScript, and it has cost companies millions of dollars in downtime.
​Early in my career, I loved the freedom of JavaScript. No types, no compilation steps, just move fast and break things. And for hackathons or side projects, that’s fine.
​But when I started building Enterprise Applications—systems with 50+ engineers, thousands of files, and complex data structures—that freedom turned into chaos.
​Here is why, in 2026, I consider TypeScript a strict requirement for any serious project.
​1. Documentation That Never Lies
​In JavaScript, you rely on comments or external documentation to know what an object looks like.
// user object has a name and id
​But developers are human. We change the code, but we forget to update the comments. Six months later, a new hire tries to access user.fullname, but the API changed to user.firstName. The app crashes.
​In TypeScript, the code is the documentation.
If I change an interface, every single file using that interface turns red. The compiler screams at me. It forces me to fix the documentation before I can even deploy.
​2. Refactoring Without Fear
​Enterprise software is never "finished." It is constantly changing.
Imagine renaming a core database field in a massive JavaScript codebase. You have to Ctrl+F and pray you found every instance. If you miss one? Runtime error.
​In TypeScript, I press F2 (Rename Symbol).
VS Code updates every reference across the entire project instantly. I can refactor a 100,000-line codebase with the confidence that I didn't break anything.
​3. "It Slows Me Down" is a Myth
​The biggest complaint I hear is: "Writing types takes too much time."
​Let’s be real: You are going to spend time on types regardless.
​With TypeScript: You spend that time while coding.
​With JavaScript: You spend that time debugging in production.
​I would rather spend 5 extra minutes defining an interface today than spend 5 hours fixing a critical bug on a Saturday night.
​4. The "Bus Factor"
​If your lead engineer leaves tomorrow, can a new developer understand their JavaScript code? Probably not without asking a lot of questions. "Is this variable a string or a number? What does this function return?"
​With TypeScript, the new developer hovers over the variable, and the IDE tells them exactly what it is. It drastically reduces onboarding time.
​The Verdict
​JavaScript is for prototyping. TypeScript is for engineering.
​If you are building a throwaway script, use JS. But if you are building a product that handles real money and real users, TypeScript isn't a "nice to have." It is your insurance policy.
​Hi, I'm Frank Oge. I build high-performance software and write about the tech that powers it. If you enjoyed this, check out more of my work at frankoge.com