According to Nintendo Support Center [1]https://en-americas-support.nintendo.com/app/answers/detail/a_id/22361/kw/charge%20joy%20con, it takes approximately 3 and a half hours in order for the Nintendo Switch Joy-Con Controller to fully charge. This applies to Nintendo Switch Family (Nintendo Switch & Nintendo Switch Lite).
If you are wondering how long does it take to fully charge a Nintendo Switch Pro Controller, you can find it here.