Quick Fix: In your tsconfig.json, configure experimentalDecorators as true and useDefineForClassFields as false to properly utilize decorators in Lit.
The Problem:
A developer is creating a LitElement in TypeScript, but encounters errors related to the @customElement() and @property() decorators. The developer is getting a runtime error indicating that class fields like ‘name’ are set using class fields instead of accessors, and IDE errors indicating issues with the decorators’ signatures. The developer seeks assistance in resolving these issues and making the code work as expected.
The Solutions:
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Solution 1: Updated answer for Lit 3.0
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For Lit versions 3 and above, utilize standard decorators with the accessor keyword. Update tsconfig.json with the default settings for experimentalDecorators and useDefineForClassFields. For instance, modify the name property in your code to:
Ensure you follow the guidelines provided in Lit’s documentation for decorators: https://lit.dev/docs/components/decorators/#decorators-typescript. In your TypeScript tsconfig.json file, set experimentalDecorators to true and useDefineForClassFields to false. This will allow decorators to work correctly with Lit.
Q&A
Why do I encounter property decorator issues when writing TS based Lit-Elements with decorators that are defined in lit-decorators.js
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Make sure that experimental decorator and useDefileForClassFields are set.
How to apply the standard decorators in Lit version 3 or higher
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Use the accessor on the property instead of decorators.
Where to get guidance for the decorator use in Lit
The following video, titled "25. Just...One...More...Fix... | Typescript #typescript #javascript ...", provides additional insights and in-depth exploration related to the topics discussed in this post.
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