Hi vijayakumar,
This issue seems to be related to this older forum post https://community.mendix.com/link/questions/107378
I will say that a member of my team currently experiences this issue for login and various page views on all versions of Mendix 9 and none of the solutions in the linked post worked for them. So hopefully that is not the case for you, but it does seem like this issue is computer/hardware specific.
If it is only happening on the js code tab, a quick solution is to just edit the javascript file directly in the directory of the project inside of the javascriptsource folder.
Hope something here helps you move forward
Cheers,
Danny Kumpf