No, it doesn’t affect your credit in any way. You are just borrowing money from yourself and paying yourself back, usually with interest. Whether you should borrow it is widely debated. If you are making a good return on your investment, you are losing that increase in the value until the loan is paid back. A regular loan may cost you less if you can get an interest rate lower than what you are making on the 401K, plus it will help build your credit.

Apply within your company, ask the Finance department.
In most cases you can borrow up to 50 grand or 50% of the balance, whichever is smaller.

Advantages: quick cash, no credit approval process, low interest rate, and you avoid 10% penalties if you were to withdraw(income taxes)
Disadvantages: slowing growth of retirement fund, consider your age. If you’re somewhat young, go for it, if you have a stable predictable income. Also, payback is through payroll deduction, consider smaller future income(net not gross)

Use this method as a last resort, it will not build credit…in fact you’re probably better off with a regular bank loan.