TypeScript 5.9 ships import defer and node20

Summary

Deferred imports let you defer expensive initialization and improve startup performance. node20 gives a stable module target that won't change, replacing the moving target of nodenext.

Why it matters

Deferred imports let you defer expensive initialization and improve startup performance. node20 gives a stable module target that won't change, replacing the moving target of nodenext.

Sources

1. 1.The key benefit of import defer is that the module is only evaluated when one of its exports is first accessed.
2. 2.import defer will only work under the --module modes preserve and esnext.
3. 3.TypeScript 5.9 brings a stable option for these settings called node20, intended to model the behavior of Node.js v20.
4. 4.This feature is particularly useful for conditionally loading modules with expensive or platform-specific initialization. It can also improve startup performance by deferring module evaluation for app features until they are actually needed.