https://www.d-scolle.net/core/2.6/ip_libs/js/hpb/responsive.js

1IPAD_LAMDSCAPE           = 1024;
2IPAD_PORTRAIT            = 768;
3IPAD_THEME_B_DUMMY_WIDTH = 1228;
4IS_THEME_B               = $("#theme_b_flg").val() == null ? false : true;
5
6$(function(){
7    var TARGET_SET = [
8      {size: {portrait: 320, landscape: 640}, targets: [
9          ['Android', 'Mobile'],
10//          ['Android 4', 'ISW13HT', 'Chrome'],
11//          ['Android 4', 'SonySO-02E', 'Chrome'],
12//          ['Android 4', 'SC-06D', 'Chrome'],
13//          ['Android 4', 'SC-04E', 'Chrome'],
14//          ['Android 4', '202F', 'Mobile Safari'],
15//          ['Android 4', 'SC-01F', 'Chrome'], // Galaxy note 3
16//          ['Android 4', 'SC-02F', 'Chrome'], // Galaxy J
17//          ['Android 4', '304SH', 'Chrome'],  // Galaxy J
18        ],device_type: 'Android'},
19      {size: {portrait: IPAD_PORTRAIT, landscape:IPAD_LAMDSCAPE }, targets: [
20          ['Mac OS X', 'iPad', 'Safari'],
21        ], device_type: 'iPad'},
22      {size: {portrait: 'device-width', landscape:'device-height' }, targets: [
23          ['Mac OS X', 'iPhone', 'Safari'],
24        ],device_type: 'iPhone'},
25    ];
26
27    var ua = navigator.userAgent;
28    var o = Math.abs(window.orientation) !== 90 ? 'portrait' : 'landscape';
29    for (var i in TARGET_SET) {
30      var set = TARGET_SET[i];
31      for (var j in set.targets) {
32        var elements = set.targets[j];
33        var cnt = 0;
34        var matched = 0;
35
36        for (var k in elements) {
37          var element = elements[k];
38          if (ua.indexOf(element) !== -1) {
39            matched++;
40          }
41          cnt++;
42        }
43        
44        var attr    = '';
45
46        if (cnt === matched) {
47          // for iPhone
48          if(set.device_type == 'iPhone'){
49              attr = 'width=device-width';
50          }
51          // for iPad theme_b.
52          else if(set.device_type == 'iPad' && IS_THEME_B){
53              attr = 'width=' + IPAD_THEME_B_DUMMY_WIDTH;
54          }
55          // for other.
56          else{
57              attr = 'width=' + set.size[o] + ' ,initial-scale=1.0,  maximum-scale=1.0';
58          }
59          // rewrite meta tag. 
60          $("meta[name='viewport']").attr('content', attr);
61          return;
62        }
63      }
64    }
65});