[rokweom]

Nowadays most basic LED bulbs just put the LEDs in series to get the combined voltage drop close to the rectified and filtered mains voltage, and a linear regulator takes care of the rest. This is cheaper and simpler than other methods mentioned by other users (switching or capacitive dropper). Here's a nice video with a schematic and even a way to hack them to lower the power: https://youtu.be/5HTa2jVi_rc (feel free to skip around, no need to watch the whole video to understand it)