Nowadays we usually reserve the word "electronics" for devices with chips in them, broadly speaking. Devices with heating elements or non-miniature motors are usually not electronics in this sense of the word.

Using this definition, many electronic devices made in the last twenty years work fine at 120V or 240V. Their power supplies always have the input voltage printed on them, though you may need a magnifying glass to read it. Typically you'll see "100-240V 50-60 Hz".

Devices with motors usually won't work if connected to the wrong input voltage. If the voltage is too high, their motors will burn out almost immediately; if it's too low, they may operate but very slowly and will often overheat.

Devices with heating elements will burn out immediately if connected to too high a voltage. Some such devices are wired to allow either 120V or 240V operation, with a switch to select the voltage. If the switch is in the 120V position and you plug your travel hair dryer into a 240V outlet, you'll need a new hair dryer.