Improve regex detection in JS (#1473)

The pattern for regular expressions in JS now also matches empty character
sets and it handles expressions like `/[\]/]/` now correctly.

Author: RunDevelopment

components/prism-javascript.js

@@ -23,7 +23,7 @@ Prism.languages.javascript['class-name'][0].pattern = /(\b(?:class|interface|ext
 
 Prism.languages.insertBefore('javascript', 'keyword', {
 	'regex': {
-		pattern: /((?:^|[^$\w\xA0-\uFFFF."'\])\s])\s*)\/(\[[^\]\r\n]+]|\\.|[^/\\\[\r\n])+\/[gimyu]{0,5}(?=\s*($|[\r\n,.;})\]]))/,
+		pattern: /((?:^|[^$\w\xA0-\uFFFF."'\])\s])\s*)\/(\[(?:[^\]\\\r\n]|\\.)*]|\\.|[^/\\\[\r\n])+\/[gimyu]{0,5}(?=\s*($|[\r\n,.;})\]]))/,
 		lookbehind: true,
 		greedy: true
 	},

components/prism-javascript.min.js

@@ -738,7 +738,7 @@ Prism.languages.javascript['class-name'][0].pattern = /(\b(?:class|interface|ext
 
 Prism.languages.insertBefore('javascript', 'keyword', {
 	'regex': {
-		pattern: /((?:^|[^$\w\xA0-\uFFFF."'\])\s])\s*)\/(\[[^\]\r\n]+]|\\.|[^/\\\[\r\n])+\/[gimyu]{0,5}(?=\s*($|[\r\n,.;})\]]))/,
+		pattern: /((?:^|[^$\w\xA0-\uFFFF."'\])\s])\s*)\/(\[(?:[^\]\\\r\n]|\\.)*]|\\.|[^/\\\[\r\n])+\/[gimyu]{0,5}(?=\s*($|[\r\n,.;})\]]))/,
 		lookbehind: true,
 		greedy: true
 	},

prism.js

@@ -2,7 +2,9 @@
 /foo/gimyu,
 /[\[\]]{2,4}(?:foo)*/;
 /foo"test"bar/;
-/foo\//
+/foo\//;
+/[]/;
+/[\]/]/;
 1 / 4 + "/, not a regex";
 / '1' '2' '3' '4' '5' /
 [/foo/]
@@ -14,12 +16,14 @@
 	["regex", "/foo/gimyu"], ["punctuation", ","],
 	["regex", "/[\\[\\]]{2,4}(?:foo)*/"], ["punctuation", ";"],
 	["regex", "/foo\"test\"bar/"], ["punctuation", ";"],
-	["regex", "/foo\\//"],
+	["regex", "/foo\\//"], ["punctuation", ";"],
+	["regex", "/[]/"], ["punctuation", ";"],
+	["regex", "/[\\]/]/"], ["punctuation", ";"],
 	["number", "1"], ["operator", "/"], ["number", "4"], ["operator", "+"], ["string", "\"/, not a regex\""], ["punctuation", ";"],
 	["regex", "/ '1' '2' '3' '4' '5' /"],
 	["punctuation", "["], ["regex", "/foo/"], ["punctuation", "]"]
 ]
 
 ----------------------------------------------------
 
-Checks for regex.
+Checks for regex.