Phil Nash

4 Steps from JavaScript to TypeScript

Migrate from JavaScript to TypeScript without the risky rewrite. This talk provides a practical, four-step blueprint for adopting it at your own pace.

4 Steps from JavaScript to TypeScript
#1about 4 minutes

Evaluating the pros and cons of TypeScript adoption

Consider the benefits of type safety and improved tooling against the costs of a learning curve and build overhead before migrating a project.

#2about 3 minutes

Step 1: Enable TypeScript type checking for JavaScript files

Use editor settings like `checkJs` or a `// @ts-check` comment to get immediate type feedback on your JavaScript code without any build changes.

#3about 5 minutes

Step 2: Introduce the TypeScript compiler with a minimal setup

Add TypeScript as a dependency and configure `tsconfig.json` with non-strict settings like `allowJs` to compile existing JavaScript without errors.

#4about 3 minutes

Step 3: Enable build-time type checking for JavaScript files

Activate `checkJs` in your `tsconfig.json` to enforce type safety during the build and install necessary `@types` packages for dependencies.

#5about 4 minutes

Leverage JS Doc for type safety in JavaScript

Add types to your JavaScript project using JS Doc comments, allowing TypeScript to provide strong typing without converting files to `.ts`.

#6about 5 minutes

Step 4: Incrementally convert JavaScript files to TypeScript

Gradually rename `.js` files to `.ts` one at a time, updating syntax from CommonJS to ES Modules and adding explicit types as you go.

#7about 2 minutes

Recap of the four-step JavaScript to TypeScript migration

Review the complete migration path, from enabling editor checks and introducing the compiler to incrementally converting files and adding types.

#8about 2 minutes

How to convince your team to adopt TypeScript

Demonstrate the value of TypeScript by enabling `checkJs` on an existing project to reveal hidden type-related issues as a practical proof point.

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