Storage polyfill

gistfile1.js

if (typeof window.localStorage == 'undefined' || typeof window.sessionStorage == 'undefined') (function () {

var Storage = function (type) {
  function createCookie(name, value, days) {
    var date, expires;

    if (days) {
      date = new Date();
      date.setTime(date.getTime()+(days*24*60*60*1000));
      expires = "; expires="+date.toGMTString();
    } else {
      expires = "";
    }
    document.cookie = name+"="+value+expires+"; path=/";
  }

  function readCookie(name) {
    var nameEQ = name + "=",
        ca = document.cookie.split(';'),
        i, c;

    for (i=0; i < ca.length; i++) {
      c = ca[i];
      while (c.charAt(0)==' ') {
        c = c.substring(1,c.length);
      }

      if (c.indexOf(nameEQ) == 0) {
        return c.substring(nameEQ.length,c.length);
      }
    }
    return null;
  }
  
  function setData(data) {
    data = JSON.stringify(data);
    if (type == 'session') {
      window.name = data;
    } else {
      createCookie('localStorage', data, 365);
    }
  }
  
  function clearData() {
    if (type == 'session') {
      window.name = '';
    } else {
      createCookie('localStorage', '', 365);
    }
  }
  
  function getData() {
    var data = type == 'session' ? window.name : readCookie('localStorage');
    return data ? JSON.parse(data) : {};
  }


  // initialise if there's already data
  var data = getData();

  return {
    length: 0,
    clear: function () {
      data = {};
      this.length = 0;
      clearData();
    },
    getItem: function (key) {
      return data[key] === undefined ? null : data[key];
    },
    key: function (i) {
      // not perfect, but works
      var ctr = 0;
      for (var k in data) {
        if (ctr == i) return k;
        else ctr++;
      }
      return null;
    },
    removeItem: function (key) {
      delete data[key];
      this.length--;
      setData(data);
    },
    setItem: function (key, value) {
      data[key] = value+''; // forces the value to a string
      this.length++;
      setData(data);
    }
  };
};

if (typeof window.localStorage == 'undefined') window.localStorage = new Storage('local');
if (typeof window.sessionStorage == 'undefined') window.sessionStorage = new Storage('session');

})();

I've combined the ideas from @hasdavidc and @yehosef to account for the non existence of webstorage in older browsers and to accommodate for Safari's private browsing.

I've also tweaked the sessionStorage code so that it acts independent of the localStorage and is unique per window per tab to mimic the native behaviour.

See https://gist.github.com/jarrodirwin/0ce4c0888336b533b2c4

hello sir,,
i am quite new in web development..
i just wanted to make a website which can fetch users data and save it locally, using their cookies,..
so how can i do this..
language known by me- c,js,html5,css,jquery

Great job!