how can I disable the system print dialog?

[tripower]

Hello

how is it possible to disable the system print dialog?
I found a flag in Firefox => print.prefer_system_dialog
but can I set it also by js code?
because I use the library (pdf.js, viewer.js => v3.xx) in my Electron App
and here always the system print dialog is shown :(

thanks in advance

Greetings
Klaus