https://conz-tokyo.com/js/C/sys/select_ajax_subject.js

1jQuery(document).ready(function() {
2    var subjectSelect = jQuery('.block-inquiry--subject select[name="subject_id"]');
3    if (!jQuery(".block-inquiry--brand [name='brand'] option:selected").val()) {
4        subjectSelect.empty();
5        subjectSelect.append(jQuery('<option>', { 
6            value: '',
7            text: 'お問い合わせ先ブランドを選択してください。'
8        }));
9    }
10    jQuery('.block-inquiry--brand select[name="brand"]').change(function() {
11        var selectedBrand = jQuery(this).val();
12        
13        if (selectedBrand) {
14            jQuery.ajax({
15                url: EC_WWW_ROOT + "/shop/contact/subjectajax.aspx",
16                type: 'GET',
17                data: { brand: selectedBrand },
18                dataType: 'json',
19                success: function(response) {
20                    var subjectSelect = jQuery('.block-inquiry--subject select[name="subject_id"]');
21                    
22                    subjectSelect.empty();
23                    
24                    subjectSelect.append(jQuery('<option>', { 
25                        value: '',
26                        text: '選択してください。'
27                    }));
28                    
29                    jQuery.each(response.InnerElements, function(index, item) {
30                        var value = '';
31                        var text = '';
32
33                        jQuery.each(item.Attributes, function(_, attr) {
34                            if (attr.Key === 'value') {
35                                value = attr.Value;
36                            }
37                        });
38
39                        text = item.InnerText;
40
41                        subjectSelect.append(jQuery('<option>', { 
42                            value: value,
43                            text: text
44                        }));
45                    });
46                },
47            });
48        } else {
49            var subjectSelect = jQuery('.block-inquiry--subject select[name="subject_id"]');
50            subjectSelect.empty();
51            subjectSelect.append(jQuery('<option>', { 
52                value: '',
53                text: 'お問い合わせ先ブランドを選択してください。'
54            }));
55        }
56    });
57});