select 2 code example

Example 1: get value select 2

//get selected value
$('#mySelect2').find(':selected').val();

Example 2: select2

$('.js-example-basic-single').select2({
  placeholder: 'Select an option'
});

Example 3: select 2 select a value

SELECT2 V4 :
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For select2 v4 you can append directly an option/s as follow:

<select id="myMultipleSelect2" multiple="" name="myMultipleSelect2[]">
    <option value="TheID" selected="selected">The text</option>                                                                   
</select>

Or with JQuery:
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var $newOption = $("<option selected='selected'></option>").val("TheID")
					.text("The text")
 
$("#myMultipleSelect2").append($newOption).trigger('change');

other example :
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$("#myMultipleSelect2").val(5).trigger('change');