Check if selected dropdown value is empty using jQuery

You need to use .change() event as well as using # to target element by id:

$('#EventStartTimeMin').change(function() {
    if($(this).val()===""){ 
        console.log('empty');    
    }
});

Fiddle Demo

You forgot the # on the id selector:

if ($("#EventStartTimeMin").val() === "") {
    // ...
}

You can try this also-

if( !$('#EventStartTimeMin').val() ) {
// do something
}