function space_trim(str)
	{
		if(!str || str.length <= 0) return "";
		
		var hel_str = str;
		try
		{
			while(hel_str.substring(0,1) == " ")
			{
				hel_str = hel_str.substring(1,hel_str.length);    //去掉首部空格
			}
			while(hel_str.substring(hel_str.length-1,hel_str.length) == " ")
			{
				hel_str = hel_str.substring(0,hel_str.length-1);  //去掉尾部空格
			}
		}catch(e){}
		
		return hel_str;
	}