Here's the decision procedure:
If there's no collateral damage and the JS is clear (e.g. 28 --> Math.pow(2, 8)): do it.
If there's no proper way to express the JS in Python (e.g. instanceof and typeof keywords): do it
If it's really important (only "print" and "self"): do it
Else: DON'T
These few special cases that mess with your code are all mentioned in a section on the the main page.
And you can easily remove them from the transformations if you want.