Returns a sequence constructed by inserting an item or a sequence of items at a given position within an existing sequence.
fn:insert-before( $target as item()*,$position as xs:integer,$inserts as item()*item()*The value returned by the function consists of all items of $target whose
index is less than $position, followed by all items of
$inserts, followed by the remaining elements of $target, in
that order.
let $abc := ("a", "b", "c")
The expression fn:insert-before($abc, 0, "z") returns ("z", "a", "b", "c").
The expression fn:insert-before($abc, 1, "z") returns ("z", "a", "b", "c").
The expression fn:insert-before($abc, 2, "z") returns ("a", "z", "b", "c").
The expression fn:insert-before($abc, 3, "z") returns ("a", "b", "z", "c").
The expression fn:insert-before($abc, 4, "z") returns ("a", "b", "c", "z").
If $target is the empty sequence, $inserts is returned. If
$inserts is the empty sequence, $target is returned.
If $position is less than one (1), the first position, the effective value
of $position is one (1). If $position is greater than the
number of items in $target, then the effective value of
$position is equal to the number of items in $target plus
1.
The value of $target is not affected by the sequence construction.