get multiple selected value of select2 dropdown in jquery code example

Example 1: jquery select2 multiple select all

$("#checkbox").click(function(){
    if($("#checkbox").is(':checked') ){
        $("select > option").prop("selected","selected");
    }else{
        $("select > option").removeAttr("selected");
     }
});

Example 2: select2 multi select get selected value

alert("Selected value is: "+$(".leaderMultiSelctdropdown").select2("val"));

alternatively, if you used a regular selectbox as base, you should be able to
use the normal jquery call, too:

alert("Selected value is: "+$(".leaderMultiSelctdropdown").val());