Ninja Forms 3 doesn’t come built in with a password field, which makes things like user registration with Ninja Forms, a bit less user-friendly.
Save the JS gist above in a child theme in the following directory:
Then add the PHP script to your theme’s functions.php file (without the starting PHP tag in the file of course!)
That should convert your plain text password from Ninja Forms into a password field on the front-end, and it should work across browsers too. You can see how it might appear in the JSFiddle here.