JSFiddle - React, Tailwind, and code Playground

HTML

<select id="regions" name="regions">
    <option value="hint">Region</option>
    <option value="0">1-3</option>
    <option value="1">4-6</option>
    <option value="2">7-9</option>
</select>

<select id="numbers">
</select>

JavaScript

$(function() {
    var regions = $('#regions'),
        numbers = $('#numbers').hide(),
        nums = [
            [1, 2, 3],
            [4, 5, 6],
            [7, 8, 9]
        ];
    
    regions.change(function() {
        if(this.value === 'hint') {
            numbers.hide();
            return;
        }
        
        var val = parseInt(this.value);
        
        if(val >= 0 && val <= 2) {
            numbers.empty();
            
            for(var i = 0; i < nums[val].length; i++) {
                $('<option value="' + nums[val][i] + '">' + nums[val][i] + '</option>').appendTo(numbers);
            }
            
            numbers.show();
        } else {
            numbers.hide();
        }
    });
    
});