The last TypeScript release built on JavaScript
TypeScript 6.0 is the last release built on JavaScript — and the bridge to TypeScript 7.0, which is being rewritten in Go for native speed and parallel type-checking. This release modernizes defaults (strict mode on, ESM-first, ES2025 target), adds built-in Temporal API types, Map.getOrInsert, and RegExp.escape, and deprecates legacy patterns that won't survive the native port. If you write TypeScript, the migration window to the native era starts now.