create new thread at main process but get SyntaxError: Cannot use import statement outside a module

[DeepJoyPo]

My app is built on quasar + electron + vue。And I have two questions:

1. In electron-main.ts, I have esm import statements and cjs import statements(require). How does this work? I think generally mixing use these two types is not allowed.
2. The main problem is I want to create a new thread by the electron main thread, but I get error: SyntaxError: Cannot use import statement outside a module. I don't know why this happened. As I mention above, I already use esm import statements in electron-main.ts and all goes well. It seems that the new thread detaches from the frame context and looks for the package.js
   So, what's the magic here?