The deprecated compile() method is used to (re-)compile a regular expression during execution of a script. It is basically the same as the RegExp constructor.
The non-standard lastMatch property is a static and read-only property of regular expressions that contains the last matched characters. RegExp.$& is an alias for this property.
The non-standard lastParen property is a static and read-only property of regular expressions that contains the last parenthesized substring match, if any. RegExp.$+ is an alias for this property.
The non-standard leftContext property is a static and read-only property of regular expressions that contains the substring preceding the most recent match. RegExp.$` is an alias for this property.
The non-standard $1, $2, $3, $4, $5, $6, $7, $8, $9 properties are static and read-only properties of regular expressions that contain parenthesized substring matches.
The non-standard rightContext property is a static and read-only property of regular expressions that contains the substring following the most recent match. RegExp.$' is an alias for this property.
The sticky property reflects whether or not the search is sticky (searches in strings only from the index indicated by the lastIndex property of this regular expression). sticky is a read-only property of an individual regular expression object.
The unicode property indicates whether or not the "u" flag is used with a regular expression. unicode is a read-only property of an individual regular expression instance.