JAVASCRIPT

select2 placeholder

$(".js-example-placeholder-single").select2({
    placeholder: "Select a state",
    allowClear: true
});

select placeholder

// A non-CSS - no JavaScript/jQuery answer: 
// add option and disable it, it will act like placeholder.  
<select>
    <option value="" disabled selected>Select your option</option>
    <option value="optionA">optionA</option>
</select>