Answers for "select2 select option"

select2 clear options

Remove the selected options : 
-----------------------------
$('#mySelect2').val(null).trigger('change');

============================================

Completly remove the select2 initialization :
--------------------------------------------
$('#payment_method').html('').select2({data: [{id: '', text: ''}]});

select2 add option

// Set the value, creating a new option if necessary
if ($('#mySelect2').find("option[value='" + data.id + "']").length) {
    $('#mySelect2').val(data.id).trigger('change');
} else { 
    // Create a DOM Option and pre-select by default
    var newOption = new Option(data.text, data.id, true, true);
    // Append it to the select
    $('#mySelect2').append(newOption).trigger('change');
}

select2 multi select

######## In your HTML:
<select class="js-example-basic-multiple" name="states[]" multiple="multiple">
  <option value="AL">Alabama</option>
    ...
  <option value="WY">Wyoming</option>
</select>

####### In your Javascript (external .js resource or <script> tag):
$(document).ready(function() {
    $('.js-example-basic-multiple').select2();
});

######### Get Selected values
$('.js-example-basic-multiple').select2('val')

######## Pre select values on page loads
 $('.js-example-basic-multiple').val(['AL', 'WY']).trigger('change');

select2

$(".js-example-basic-multiple-limit").select2({
  maximumSelectionLength: 3
});

select2 .select2-results .select2-highlighted

<span id="menuOption1-container">
    <select id="menuOption1"> 
        <option value="1"> One </option>
        <option value="2"> Two </option>
        <option value="3"> Three </option>
        <option value="4"> Four </option>
        <option value="5"> Five </option>
    </select>
</span>

<span id="menuOption2-container">
    <select id="menuOption2"> 
        <option value="a"> Vowel a </option>
        <option value="e"> Vowel e </option>
        <option value="i"> Vowel i </option>
        <option value="o"> Vowel o </option>
        <option value="o"> Vowel u </option>
    </select>
</span>

select2 .select2-results .select2-highlighted

#menuOption1-container  .select2-results__option--highlighted {
    background-color: #50831F !important;
}

#menuOption2-container  .select2-results__option--highlighted {
   background-color: #28915F !important;
}