found in below
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.
mark()
and
.
addMark()
this api is similar to addBack() ; but a great different improve,
more information,
(A) add a mark to a set of matched elements, using .mark(
your_any_Label )
(B) pick up a set of matched elements, using .addMark(
your_any_Label )
this A api not change anything on the current set of matched elements,
just leave a mark.
when you decide somewhere to add a set of matched elements, just call
its marked " label".
in this line, this set of matched elements of selector1 has been picked
up and add into the current set of matched elements of selector2.
in other way, a same meaning is$(selector2).add(
$(selector1) );