Basic
Use select2() function on select element to convert it to Select 2.
<select class="form-control  basic">
    <option selected="selected">orange</option>
    <option>white</option>
    <option>purple</option>
</select>
                                        
var ss = $(".basic").select2({
    tags: true,
});
                                        Small Select2
Use data('select2') function to get container of select2.
<select class="form-control form-small">
    <option selected="selected">orange</option>
    <option>white</option>
    <option>purple</option>
</select>
                                        
var formSmall = $(".form-small").select2({ tags: true });
formSmall.data('select2').$container.addClass('form-control-sm')
                                        Nested
Add options inside the optgroups to for group options.
<select class="form-control nested">
    <optgroup label="Group1">
        <option selected="selected">orange</option>
        <option>white</option>
        <option>purple</option>
    </optgroup>
    <optgroup label="Group2">
        <option>purple</option>
        <option>orange</option>
        <option>white</option>
    </optgroup>
    <optgroup label="Group3">
        <option>white</option>
        <option>purple</option>
        <option>orange</option>
    </optgroup>
</select>
                                        
$(".nested").select2({
    tags: true
});
                                        Disabling options
Disable Select using disabled attribute.
<select class="form-control disabled-results">
    <option value="one">First</option>
    <option value="two" disabled="disabled">Second</option>
    <option value="three">Third</option>
</select>
                                        
$(".disabled-results").select2();
                                        Placeholder
Apply Placeholder by setting option placeholder option.
<select class="placeholder js-states form-control">
    <option>Choose...</option>
    <option value="one">First</option>
    <option value="two">Second</option>
    <option value="three">Third</option>
    <option value="four">Fourth</option>
    <option value="five">Fifth</option>
</select>
                                        
$(".placeholder").select2({
    placeholder: "Make a Selection",
    allowClear: true
});
                                        Tagging with multi-value select boxes
Set tags: true to convert select 2 in Tag mode.
<select class="form-control tagging" multiple="multiple">
    <option>orange</option>
    <option>white</option>
    <option>purple</option>
</select>
                                        
$(".tagging").select2({
    tags: true
});
                                        Limiting the number of Tagging
Set maximumSelectionLength: 2 with tags: true to limit selectin in Tag mode.
<select class="form-control tagging" multiple="multiple">
    <option>orange</option>
    <option>white</option>
    <option>purple</option>
</select>
                                        
var ss = $(".basic").select2({
    tags: true,
});
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