Lesson overview · Free interview practice

Migration strategies

Learn JavaScript to TypeScript migration strategies.

Topics in the full lesson
  • Introduction to Migration
  • Planning the Migration
  • Setting Up the TypeScript Environment
  • Migrating JavaScript Files
  • Incremental Adoption Techniques
  • Dealing with Any Types
  • Leveraging JSDoc Annotations
  • Refactoring and Code Improvements
  • Automated Tools and Linters
  • Testing During Migration
  • Best Practices
  • Exercises

Practice Problems

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TheoryEasy

The Rename Path: From `.js` to `.ts`

Question

How does the rename-from-.js-to-.ts migration path work? What's the order, and what should you watch out for?

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TheoryEasy

`allowJs`, `checkJs`, and the JSDoc Path

Question

What do the allowJs and checkJs flags do, and how does the JSDoc-based migration path work?

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TheoryMedium

Incremental Migration: Strategies for Adopting TypeScript

Question

What's the right strategy for migrating a large JavaScript codebase to TypeScript? Show the canonical phased approach.

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TheoryMedium

Handling `any` During Migration

Question

During a migration, any proliferates as a shortcut. How do you keep it under control, and what's the trajectory from any to proper types?

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TheoryMedium

Third-Party Library Types: DefinitelyTyped and Custom `.d.ts`

Question

How do you handle untyped third-party libraries during a migration? Walk through DefinitelyTyped, library-shipped types, and writing custom .d.ts files.

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