解决方法
jsFiddle Demo
与渲染角度没有区别.但是,如果您将来要查看这些必需的元素,那么有一个值可以测试.
required
This attribute specifies that the user must fill in a value before submitting a form. It cannot be used when the type attribute is hidden,image,or a button type (submit,reset,or button). The :optional and :required CSS pseudo-classes will be applied to the field as appropriate. 07001
