I notice that I can change the opacity of a <div> in bootstrap with the class bg-opacity-50. However, as I tried to apply this class to a <btn>, it appears to me that this class does not work. I tried to invent btn-opacity-50 and use it instead, and it does not work neither.
May I know whether there is a convenient class I can use for buttons in Bootstrap that I can change the opacity easily? If not, what should I do in that case?