It is occasionally necessary to group the select content. In the past, they were controlled by programs. Today, I found that there is an optgroup property in select that can be used.
It is tested to be suitable for browsers such as firefox and ie. The only disadvantage found is that the title style after the group cannot be customized. For example: If you want to change the font attributes, it is not possible to use a normal form, but the color and size can be changed. Under ie, italics and bold
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