How to validate bootstrap select?

[fisherspoon]

Stuck with bootstrap validation issue
select. Perhaps someone came across, I will be very grateful for your help!
Example

[fisherspoon]

The only thing I came up with was a check for the length of the value (array), if someone knows a more elegant solution, please write

regionSubscribe: function(value, attributes, attributeName, options, constraints){ if(value.length > 0){ return true; }else{ return{ inclusion: { within: [true], message: "^confirm your choice" } } }