Open butterandfly opened 9 years ago
参考：http://stackoverflow.com/questions/5805059/how-do-i-make-a-placeholder-for-a-select-box 简单来说就是对option加上disable与selected
参考：http://stackoverflow.com/questions/5805059/how-do-i-make-a-placeholder-for-a-select-box 简单来说就是对option加上disable与selected