𝗧𝘆𝗽𝗲𝗦𝗰𝗿𝗶𝗽𝘁 𝟲.𝟬 𝗕𝗿𝗲𝗮𝗸𝘀 𝗕𝘆 𝗗𝗲𝘀𝗶𝗴𝗻

TypeScript 6.0 is here and it changes everything. This release is the most significant shift since version 2.x. If you rely on legacy settings, your next build will likely fail.

Three major changes will break your code:

Why this matters:

Strict Mode Previously, you had to opt in to strict mode. Now, it is the standard. About 70% of codebases will see red builds immediately. You will face errors for uninitialized properties, implicit any types, and unchecked null values.

ES5 Support Removal You can no longer target ES5 or ES3 in your tsconfig.json. The new default is ES2025. If you need to support old browsers, you must add a separate tool like Babel to your pipeline.

Module Resolution The default is no longer CommonJS. It is now ESNext. If your Node.js project relies on implicit CommonJS behavior, you must set the module setting explicitly in your config.

How to migrate without breaking your pipeline:

  1. Audit your config Do not leave settings to chance. Add explicit values for strict, target, and module in your tsconfig.json before you upgrade.

  2. Lock your version Pin your TypeScript version in your package.json. Test your current build on your existing version before you move to 6.0.

  3. Use a feature branch Install TypeScript 6.0 on a new branch. Update your target to ES2025 and set your module type clearly.

  4. Fix types incrementally Run the compiler without emitting files to see all errors. Focus on strictNullChecks and implicit any errors first.

  5. Test everything Run your full test suite. TypeScript catches type errors, but your tests catch logic errors caused by the new strictness.

TypeScript 6.0 is the final step before the version 7.0 rewrite. Version 7.0 will use a Go-native core. This means legacy support will disappear entirely.

Modernize your codebase now to avoid a crisis later.

Source: https://dev.to/davekurian/typescript-60-launches-strict-mode-by-default-and-drops-es5-support-n31