How to use tensorflow js (tfjs) from typescript?

Note that there is unfortunately no simple way to tell whether types are available in a library since type definitions can be exported in a variety of ways.

If you do npm install --save @tensorflow/tfjs, you will see that there is a node_modules/@tensorflow/tfjs/dist/index.d.ts. Additionally in the package.json for the project, there is "types": "dist/index.d.ts".

That is to say types are available for this library.

If types are not included with the package, you can check DefinitelyTyped to see if there is a third party definition available at @types/{package}. Otherwise you'll be on your own for strong typing.