/**

  * 生成指定长度的UUID

  * @param len

  * @param radix

  * @returns uuid

  * eg: createUUID(8, 2) "01001010" createUUID(8, 10) "47473046" createUUID(8, 16) "098F4D35"

  */
调用
 var num = createUUID(6, 10);

 function createUUID(len, radix) {

     var chars = '0123456789'.split('');

     var uuid = [], i;

     radix = radix || chars.length;

     if(len){

       for (i = 0; i < len; i++){

           uuid[i] = chars[0 | Math.random()*radix];

       }

     }

     return '-'+uuid.join('');

 }