What Is TypeScript and Why Do Top Development Firms Use It?

If you have looked at job postings for software developers recently, you have likely seen TypeScript listed alongside JavaScript on almost every listing. The two are related but distinct, and the difference matters to your software project. TypeScript is not just a technology preference — it is a signal about how seriously a development team takes code quality. Understanding why helps you make better decisions about who you hire and how you evaluate their work.

TypeScript was created by Microsoft in 2012 and has since become one of the most widely used programming languages in the industry. It is a superset of JavaScript, meaning every valid JavaScript program is also a valid TypeScript program — but TypeScript adds a feature that changes how software is written and maintained: static type checking.

What JavaScript Does and Where It Falls Short

JavaScript was originally designed for simple interactivity in web browsers — making buttons do things, hiding and showing content, handling form submissions. It was not designed for the kind of large, complex applications that businesses run on today.

One of JavaScript's fundamental characteristics is that it is dynamically typed. This means you can write a function that expects a number, pass it a string instead, and the program will not complain until it actually runs — and sometimes not even then. It will simply behave unexpectedly. In a small script, this is manageable. In a codebase with hundreds of thousands of lines of code and a dozen developers, it is a source of bugs that are expensive to track down and fix.

Here is a simplified example of the problem: a function is supposed to calculate a transaction total. Someone passes in a dollar amount formatted as text ("147.50") instead of a number. JavaScript will silently attempt to do arithmetic on a string, producing incorrect results. The bug might not surface until a customer notices a wrong charge — which is a bad time to discover it.

How TypeScript Solves This

TypeScript adds types to JavaScript. When you write a function in TypeScript, you declare what kind of data it expects and what kind of data it returns. The TypeScript compiler — a tool that checks your code before it runs — will flag any place where the code passes the wrong kind of data to a function. The error is caught before the program runs, not after it is in production.

This shifts an entire class of bugs from runtime discovery (discovered by users) to compile-time discovery (discovered by developers at their workstations). For business owners, the result is software that behaves more predictably and fails less often in unexpected ways.

Types also serve as documentation. When you read a TypeScript function, you can see immediately what data it works with. In JavaScript, you often have to read through the entire function body — or the code that calls it — to understand what it expects. This makes TypeScript code faster to read, easier to maintain, and safer to modify.

The Impact on Large Projects

The benefits of TypeScript become more pronounced as a codebase grows. In a small project, a developer can hold the entire system in their head and avoid the pitfalls of JavaScript's dynamic typing through discipline and familiarity. In a large project with multiple developers and years of accumulated code, that discipline alone is not enough.

TypeScript provides a safety net at scale. When a developer changes a function — adding a parameter, changing what it returns — the compiler immediately identifies every place in the codebase that calls that function incorrectly. Without TypeScript, those places might not be discovered until they fail in production.

This also makes refactoring — the process of restructuring existing code to improve it without changing its behavior — significantly safer. Developers can make changes with confidence because the type system will catch inconsistencies they introduce.

TypeScript Adoption as a Quality Signal

The question of whether a development firm uses TypeScript is a useful proxy for other questions about their work. Teams that use TypeScript have generally decided that long-term maintainability matters more than short-term development speed. They have invested in a stricter development environment because they understand that the bugs TypeScript prevents are far more expensive to fix than the time TypeScript costs.

The alternative — JavaScript without types — is not inherently irresponsible. There are projects where JavaScript makes sense. But for business-critical applications that will be maintained over time, by multiple developers, with data integrity requirements, TypeScript is the professional choice. The industry has largely converged on this view: GitHub, Airbnb, Google, Slack, and most major software companies have adopted TypeScript as their standard.

What to Ask Your Development Team

Ask whether they use TypeScript. If the answer is no, ask why — there may be a legitimate reason, but there may also not be. Ask whether the TypeScript configuration is set to strict mode, which enables the most rigorous checks. Ask what the build process looks like and whether TypeScript errors can prevent a deployment.

A team that uses TypeScript with strict settings and enforces type checking as part of their deployment process is a team that has thought carefully about code quality. That thinking will show up in the reliability and maintainability of the software they deliver.

At Routiine LLC, TypeScript is our default for every project — web, backend, and anything in between. We use strict mode. We catch type errors at build time, not in production. If you are evaluating development partners for a software project in the Dallas-Fort Worth area, we are happy to walk through our technical standards in detail. Reach out at routiine.io/contact.