string valueOf()
生成32位随机主键

   Returns:
         {string}

   Example:
         var myUUID=new UUID();
         var rowid=myUUID.valueOf();

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string toString()
生成32位随机主键

   Returns:
         {string}

   Example:
         var myUUID=new UUID();
         var rowid=myUUID.toString();

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string createUUID()
生成32位随机主键

   Returns:
         {string}

   Example:
         var myUUID=new UUID();
         var rowid=myUUID.createUUID();

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