Choosing TypeScript Over JavaScript for New Services

architecturetypescriptdeveloper-experience

Context

Our team was starting development on a new set of microservices. We needed to decide whether to use TypeScript or JavaScript for the codebase.

Decision

Adopt TypeScript as the standard for all new backend services

Alternatives Considered

Continue using JavaScript with JSDoc comments

Pros
  • No build step required
  • Team already familiar with JavaScript
  • Faster initial development
Cons
  • JSDoc comments are not enforced
  • Limited IDE support compared to TypeScript
  • Refactoring is riskier without type safety

Use TypeScript only for critical services

Pros
  • Gradual adoption reduces learning curve
  • Can evaluate benefits before full commitment
Cons
  • Inconsistent codebase makes context switching harder
  • Shared libraries become problematic
  • Doesn't solve the refactoring problem for JS services

Reasoning

TypeScript's static typing catches bugs at compile time rather than runtime, which is especially valuable for microservices where integration issues are common. The upfront investment in learning TypeScript pays off through improved refactoring confidence, better IDE support, and reduced production bugs. The build step overhead is minimal with modern tooling.

Context and Background

We had been using JavaScript for our backend services for 3 years. While this worked well initially, we started experiencing issues as the codebase grew:

  • Refactoring was risky and time-consuming
  • Integration bugs between services were common
  • New team members struggled to understand API contracts
  • IDE autocomplete was unreliable

Implementation

We rolled out TypeScript gradually:

  1. Started with new services only
  2. Created shared TypeScript libraries for common patterns
  3. Provided team training and pair programming sessions
  4. Updated our service template to use TypeScript by default

Results After 6 Months

  • 40% reduction in production bugs related to type errors
  • Refactoring time cut in half
  • New developers report faster onboarding
  • Team satisfaction with tooling increased significantly

The decision has proven successful and we’re now considering migrating existing JavaScript services to TypeScript.

All decisions