fn.substringBefore( $input as String?, $before as String?, [$collation as String] ) as String?
Returns the substring created by taking all of the input characters that occur before the specified $before characters.
|$input||The string from which to create the substring.|
|$before||The string before which the substring is created.|
|$collation||The optional name of a valid collation URI. For information on the collation URI syntax, see the Search Developer's Guide.|
fn.substringBefore("abcdef", "def"); => abc