[jQuery] Getting checked radio button value [correct selector syntax]

[jQuery] Getting checked radio button value [correct selector syntax]


You now, I wasted three hours trying to get this work... and I tried
everything imaginable In the end, I found the following syntax (the
ONLY syntax) that worked:
$("input[@name=field-name]:checked").val();
But my question is, why dont any of the following work (they return
null values):
$("input[name='field-name']:checked").val();
$(":radio[name='field-name'][checked]").val()
$(":radio[name='field-name']:checked").val()
$("radio:checked[name='field-name']").val()
$("input:checked[name='field-name']").val()