The CSS selector that triggers the instantiation of the directive.
Angular only allows directives to trigger on CSS selectors that do not cross element boundaries.
The selector may be declared as one of the following:
element-name: select by element name.
.class: select by class name.
[attribute]: select by attribute name.
[attribute=value]: select by attribute name and value.
:not(sub_selector): select only if the element does not match the
selector1, selector2: select if either
Suppose we have a directive with an
and the following HTML:
<form> <input type="text"> <input type="radio"> <form>
The directive would only be instantiated on the
final String selector