What is Js.gen?

This file is generated by gentype, it report an error that can not find module ‘./Js.gen’ or its corresponding type declarations.

"gentypeconfig": {
    "language": "typescript",
    "shims": {"Js":"Js"},
    "generatedFileExtension": ".gen.tsx",
    "module": "commonjs",
    "debug": {
      "all": false,
      "basic": false

Have you set compilerOptions.moduleResolution to Node in your tsconfig.json ?

This usually happens to me when I don’t have Js.shim.ts file, where I re-export the types genType couldn’t find.