diff --git a/youtube_dl/utils.py b/youtube_dl/utils.py
index aed988b88..85fe1e34a 100644
--- a/youtube_dl/utils.py
+++ b/youtube_dl/utils.py
@@ -3979,18 +3979,27 @@ def js_to_json(code):
 
     def fix_kv(m):
         v = m.group(0)
+
         if v in ('true', 'false', 'null'):
             return v
         elif v.startswith('/*') or v.startswith('//') or v == ',':
             return ""
 
         if v[0] in ("'", '"'):
+
+            v = v[1:-1]
+
+            # convert Javascript's octal escape sequences (and '\0')
+            # into valid JSON escape sequences ( e.g '\347' => '\u00e7', '\0' => '\u0000' )
+            # regex based on https://mathiasbynens.be/notes/javascript-escapes
+            v = re.sub(r'\\([0-7]{1,3})', lambda x: "\\u%04x" % int(x.group(1), 8), v)
+
             v = re.sub(r'(?s)\\.|"', lambda m: {
                 '"': '\\"',
                 "\\'": "'",
                 '\\\n': '',
                 '\\x': '\\u00',
-            }.get(m.group(0), m.group(0)), v[1:-1])
+            }.get(m.group(0), m.group(0)), v)
 
         for regex, base in INTEGER_TABLE:
             im = re.match(regex, v)
@@ -4001,8 +4010,8 @@ def js_to_json(code):
         return '"%s"' % v
 
     return re.sub(r'''(?sx)
-        "(?:[^"\\]*(?:\\\\|\\['"nurtbfx/\n]))*[^"\\]*"|
-        '(?:[^'\\]*(?:\\\\|\\['"nurtbfx/\n]))*[^'\\]*'|
+        "(?:[^"\\]*(?:\\\\|\\['"nurtbfx/\n]?))*[^"\\]*"|
+        '(?:[^'\\]*(?:\\\\|\\['"nurtbfx/\n]?))*[^'\\]*'|
         {comment}|,(?={skip}[\]}}])|
         (?:(?<![0-9])[eE]|[a-df-zA-DF-Z_])[.a-zA-Z_0-9]*|
         \b(?:0[xX][0-9a-fA-F]+|0+[0-7]+)(?:{skip}:)?|