Very often your expression will use selector filters such as foo: This plugin provides custom selectors for that purpose. Makes the element required.

An expression String that is evaluated in the context of the element's form, making the field required only if the expression returns more than one element. The function is executed with the element as it's only argument: If it returns true, the element is required.

Works with text inputs, selects, checkboxes and radio buttons. Makes "field" always required.

Nothing and blanks are invalid. Makes the fruit select required.

Validation of radio button group using jQuery validation plugin - Stack Overflow

Makes the gender radio buttons required. Makes the agree checkbox required. Makes details required only if other is checked. Makes "parent" required only if age is below Proudly powered by WordPress.