https://360stories.com/localstorage.js

1const hasLocalStorage = (function(){
2    try {
3        localStorage.setItem('mod', 'mod');
4        localStorage.removeItem('mod');
5        return true;
6    } catch(e) {
7        return false;
8    }
9})()
10
11if (!hasLocalStorage) {
12    (function () {
13        var Storage = function (type) {
14            function createCookie(name, value, days) {
15                var date, expires;
16
17                if (days) {
18                    date = new Date();
19                    date.setTime(date.getTime()+(days*24*60*60*1000));
20                    expires = "; expires="+date.toGMTString();
21                } else {
22                    expires = "";
23                }
24                document.cookie = name+"="+value+expires+"; path=/";
25            }
26
27            function readCookie(name) {
28                var nameEQ = name + "=",
29                    ca = document.cookie.split(';'),
30                    i, c;
31
32                for (i=0; i < ca.length; i++) {
33                    c = ca[i];
34                    while (c.charAt(0)==' ') {
35                        c = c.substring(1,c.length);
36                    }
37
38                    if (c.indexOf(nameEQ) == 0) {
39                        return c.substring(nameEQ.length,c.length);
40                    }
41                }
42                return null;
43            }
44
45            function setData(data) {
46                // Convert data into JSON and encode to accommodate for special characters.
47                data = encodeURIComponent(JSON.stringify(data));
48                // Create cookie.
49                if (type == 'session') {
50                    createCookie(getSessionName(), data, 365);
51                } else {
52                    createCookie('localStorage', data, 365);
53                }
54            }
55
56            function clearData() {
57                if (type == 'session') {
58                    createCookie(getSessionName(), '', 365);
59                } else {
60                    createCookie('localStorage', '', 365);
61                }
62            }
63
64            function getData() {
65                // Get cookie data.
66                var data = type == 'session' ? readCookie(getSessionName()) : readCookie('localStorage');
67                // If we have some data decode, parse and return it.
68                return data ? JSON.parse(decodeURIComponent(data)) : {};
69            }
70
71            function getSessionName() {
72                // If there is no name for this window, set one.
73                // To ensure it's unquie use the current timestamp.
74                if(!window.name) {
75                    window.name = new Date().getTime();
76                }
77                return 'sessionStorage' + window.name;
78            }
79
80            // Initialise if there's already data.
81            var data = getData();
82
83            return {
84                length: 0,
85                clear: function () {
86                    data = {};
87                    this.length = 0;
88                    clearData();
89                },
90                getItem: function (key) {
91                    return data[key] === undefined ? null : data[key];
92                },
93                key: function (i) {
94                    // not perfect, but works
95                    var ctr = 0;
96                    for (var k in data) {
97                        if (ctr == i) return k;
98                        else ctr++;
99                    }
100                    return null;
101                },
102                removeItem: function (key) {
103                    delete data[key];
104                    this.length--;
105                    setData(data);
106                },
107                setItem: function (key, value) {
108                    data[key] = value+''; // forces the value to a string
109                    this.length++;
110                    setData(data);
111                }
112            };
113        };
114
115        // Replace window.localStorage and window.sessionStorage with out custom
116        // implementation.
117        var localStorage = new Storage('local');
118        var sessionStorage = new Storage('session');
119
120        Object.defineProperty(window, "localStorage", { value: localStorage })
121        Object.defineProperty(window, "sessionStorage", { value: sessionStorage })
122    })();
123}