TypeScript 5.9 ships import defer and node20
import defer defers module execution until first property access; --module node20 locks Node.js v20 behavior for stable target.
June 5, 2026
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.
Implementation verdict
Drop-in install via npm. import defer requires runtime support (preserve or esnext modules only, no downleveling). node20 replaces nodenext for projects targeting Node 20+. Worth upgrading now if you're on Node 20; import defer needs runtime support to be useful.
Sources
- 1.The key benefit of import defer is that the module is only evaluated when one of its exports is first accessed.
- 2.import defer will only work under the --module modes preserve and esnext.
- 3.TypeScript 5.9 brings a stable option for these settings called node20, intended to model the behavior of Node.js v20.
- 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.
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