Each browser provides some kind of debugging extension. Microsoft Edge provides F12 Developer Tools you can use to debug scripts in model-driven apps.
https://learn.microsoft.com/en-us/power-apps/developer/model-driven-apps/clientapi/debug-javascript-code
https://learn.microsoft.com/en-us/power-apps/developer/model-driven-apps/clientapi/reference?WT.mc_id=DX-MVP-5003911