JSFiddle - React, Tailwind, and code Playground

HTML

Array A:<div id="select_container">
<select id="select_box"></select>
</div>

Array B:<div id="array_B"></div>

Values from B which are not equal to what you selected: <div id="uniques"></div>

JavaScript

var arrA = [1, 2, 3, 4];
var arrB = [1, 5, 6, 7];
var BArrLength = arrB.length;
var i;
var selectedFromA;
var uniqueArrB = [];
var selectContainer = $('#select_container');
var htmlString = '';

$.each(arrA, function(index, value){
  htmlString += '<option value="'+value+'">'+value+'</option>';
});

$('#select_box').append('<option></option>'+htmlString);

$.each(arrB, function(index, value){
 $('#array_B').append(value);   
});

$('#select_box').html(htmlString);

$('#select_container').on('change', 'select', function(){
    selectedFromA = $('#select_box option:selected').val();
    $('#uniques').html("");
    for(i = 0; i < BArrLength; i += 1){
	    if(arrB[i] != selectedFromA){
		    $('#uniques').append(''+arrB[i]);
	    }
    }    
});