https://www.nikon.com/network/js/index.js

1(function () {
2    'use strict';
3
4    function initAreaList(areaEl, region2optionEls) {
5        var i;
6        var length;
7        var childEls = areaEl.children;
8        var optgroupEl;
9        var optionEl;
10        var documentFragment;
11        var toBeRemoved = [];
12
13        for (i = 0, length = childEls.length; i < length; i++) {
14            optgroupEl = childEls[i];
15
16            if (optgroupEl.nodeName.toUpperCase() !== 'OPTGROUP') {
17                continue;
18            }
19
20            documentFragment = document.createDocumentFragment();
21
22            while (optgroupEl.firstElementChild) {
23                optionEl = optgroupEl.firstElementChild;
24                documentFragment.appendChild(optionEl);
25            }
26
27            region2optionEls[optgroupEl.label] = documentFragment;
28            toBeRemoved.push(optgroupEl);
29        }
30
31
32        for (i = 0, length = toBeRemoved.length; i < length; i++) {
33            areaEl.removeChild(toBeRemoved[i]);
34        }
35    }
36
37    function updateAreaList(areaEl, region2optionEls, region) {
38        while (areaEl.childElementCount > 1) {
39            areaEl.removeChild(areaEl.lastElementChild); 
40        }
41
42        if (region !== '') {
43            if (!region2optionEls.hasOwnProperty(region)) {
44                throw new Error('Unexpected region value: ' + region);
45            }
46            areaEl.appendChild(region2optionEls[region].cloneNode(true));
47        }
48    }
49
50    function init() {
51        var region2optionEls = {};
52        var regionEl = document.getElementById('region');
53        var areaEl = document.getElementById('area');
54        var buttonEl = document.querySelector('.network-select__paging');
55
56        if (!regionEl || !areaEl || !buttonEl) {
57            return;
58        }
59
60        initAreaList(areaEl, region2optionEls);
61
62        regionEl.addEventListener('change', function () {
63            updateAreaList(areaEl, region2optionEls, regionEl.value);
64            areaEl.options[0].selected = true;
65        });
66
67        buttonEl.addEventListener('click', function () {
68            location.href = areaEl.value;
69        });
70
71        updateAreaList(areaEl, region2optionEls, regionEl.value);
72    }
73
74    init();
75}());