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Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
@DrAzzy
Yeah - those are opto sensors, which is what you'd probably want to use. They also make ones that have two parts, and you put them on each side of the area where things pass though to detect when something blocks the light between them.