[jsinterp] Fix `extract_object` (#13580)

Fixes sig extraction for YouTube player `e12fbea4`

Authored by: seproDev

test/test_jsinterp.py

@@ -478,6 +478,10 @@ class TestJSInterpreter(unittest.TestCase):
         func = jsi.extract_function('c', {'e': 10}, {'f': 100, 'g': 1000})
         self.assertEqual(func([1]), 1111)
 
+    def test_extract_object(self):
+        jsi = JSInterpreter('var a={};a.xy={};var xy;var zxy={};xy={z:function(){return "abc"}};')
+        self.assertTrue('z' in jsi.extract_object('xy', None))
+
     def test_increment_decrement(self):
         self._test('function f() { var x = 1; return ++x; }', 2)
         self._test('function f() { var x = 1; return x++; }', 1)

test/test_youtube_signature.py

@@ -133,6 +133,11 @@ _SIG_TESTS = [
         '2aq0aqSyOoJXtK73m-uME_jv7-pT15gOFC02RFkGMqWpzEICs69VdbwQ0LDp1v7j8xx92efCJlYFYb1sUkkBSPOlPmXgIARw8JQ0qOAOAA',
         'IAOAOq0QJ8wRAAgXmPlOPSBkkUs1bYFYlJCfe29xx8j7v1pDL0QwbdV96sCIEzpWqMGkFR20CFOg51Tp-7vj_E2u-m37KtXJoOySqa0',
     ),
+    (
+        'https://www.youtube.com/s/player/e12fbea4/player_ias.vflset/en_US/base.js',
+        'gN7a-hudCuAuPH6fByOk1_GNXN0yNMHShjZXS2VOgsEItAJz0tipeavEOmNdYN-wUtcEqD3bCXjc0iyKfAyZxCBGgIARwsSdQfJ2CJtt',
+        'JC2JfQdSswRAIgGBCxZyAfKyi0cjXCb3DqEctUw-NYdNmOEvaepit0zJAtIEsgOV2SXZjhSHMNy0NXNG_1kOyBf6HPuAuCduh-a',
+    ),
 ]
 
 _NSIG_TESTS = [

yt_dlp/jsinterp.py

@@ -857,7 +857,7 @@ class JSInterpreter:
         obj = {}
         obj_m = re.search(
             r'''(?x)
-                (?<!\.)%s\s*=\s*{\s*
+                (?<![a-zA-Z$0-9.])%s\s*=\s*{\s*
                     (?P<fields>(%s\s*:\s*function\s*\(.*?\)\s*{.*?}(?:,\s*)?)*)
                 }\s*;
             ''' % (re.escape(objname), _FUNC_NAME_RE),