Adding TypeScript to an existing Svelte project

Svelte has supported TypeScript since 2020, but integrating TypeScript into a Svelte project requires adjustments to the toolchain, typically involving a bundler like Rollup, webpack, or Parcel. The process includes configuring the bundler to convert TypeScript into JavaScript and involves setting up specific configurations for each bundler to manage TypeScript and Svelte files. The guide provides detailed instructions for configuring TypeScript with each of the three popular bundlers, highlighting Rollup's inherent compatibility with Svelte due to its origins. While Rollup is considered a reliable option due to its close integration with Svelte, webpack and Parcel are also viable with the help of third-party packages. The tutorial aims to equip developers with the knowledge to successfully migrate their projects to utilize TypeScript, emphasizing the importance of checking toolchain behavior during dependency upgrades and ensuring both TypeScript and Svelte files are correctly transpiled.