/**

 * 新浪微博mid与url互转实用工具

 * 作者: XiNGRZ (http://weibo.com/xingrz)

 */

var WeiboUtility = {};

/**

 * 62进制字典

 */

WeiboUtility.str62keys = [

 "0", "1", "2", "3", "4", "5", "6", "7", "8", "9",

 "a", "b", "c", "d", "e", "f", "g", "h", "i", "j",

 "k", "l", "m", "n", "o", "p", "q", "r", "s", "t",

 "u", "v", "w", "x", "y", "z",

 "A", "B", "C", "D", "E", "F", "G", "H", "I", "J",

 "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T",

 "U", "V", "W", "X", "Y", "Z"

];

/**

 * 62进制值转换为10进制

 * @param {String} str62 62进制值

 * @return {String} 10进制值

 */

WeiboUtility.str62to10 = function(str62) {

 var i10 = 0;

 for (var i = 0; i < str62.length; i++)

 {

  var n = str62.length - i - 1;

  var s = str62[i];

  i10 += this.str62keys.indexOf(s) * Math.pow(62, n);

 }

 return i10;

};

/**

 * 10进制值转换为62进制

 * @param {String} int10 10进制值

 * @return {String} 62进制值

 */

WeiboUtility.int10to62 = function(int10) {

 var s62 = '';

 var r = 0;

 while (int10 != 0)

 {

  r = int10 % 62;

  s62 = this.str62keys[r] + s62;

  int10 = Math.floor(int10 / 62);

 }

 return s62;

};

/**

 * URL字符转换为mid

 * @param {String} url 微博URL字符，如 "wr4mOFqpbO"

 * @return {String} 微博mid，如 "201110410216293360"

 */

WeiboUtility.url2mid = function(url) {

 var mid = '';

 for (var i = url.length - 4; i > -4; i = i - 4) //从最后往前以4字节为一组读取URL字符

 {

  var offset1 = i < 0 ? 0 : i;

  var offset2 = i + 4;

  var str = url.substring(offset1, offset2);

  str = this.str62to10(str);

  if (offset1 > 0) //若不是第一组，则不足7位补0

  {

   while (str.length < 7)

   {

    str = '0' + str;

   }

  }

  mid = str + mid;

 }

 return mid;

};

/**

 * mid转换为URL字符

 * @param {String} mid 微博mid，如 "201110410216293360"

 * @return {String} 微博URL字符，如 "wr4mOFqpbO"

 */

WeiboUtility.mid2url = function(mid) {

 if (typeof(mid) != 'string') return false; //mid数值较大，必须为字符串！

 var url = '';

 for (var i = mid.length - 7; i > -7; i = i - 7) //从最后往前以7字节为一组读取mid

 {

  var offset1 = i < 0 ? 0 : i;

  var offset2 = i + 7;

  var num = mid.substring(offset1, offset2);

  num = this.int10to62(num);

  url = num + url;

 }

 return url;

};

document.write(WeiboUtility.mid2url("3775437480334921"));