[lazaroclapp]

Depends where you live. California law renders those clauses null as long as the IP is generated outside of work, without use of employer equipment, facilities, internal knowledge or other IP already belonging to the employer. There are some potential issues if the side work "relates to the employer's business", so running any specific plan through a real lawyer is a good idea at some point. But, as far as I have heard, doing this is not uncommon when the side-project does not compete with the employer in any way.

IANAL. For specifics, see § 2870: https://leginfo.legislature.ca.gov/faces/codes_displaySectio...

Presumably some other jurisdictions have similar laws, and that is a factor in your job search if you are planning to work on anything on the side: pick a location with laws that allow this. Failing that, you can negotiate to retain IP on existing side-projects when you join a company, as an amendment to your contract.