]> jfr.im git - yt-dlp.git/blobdiff - yt_dlp/jsinterp.py
[ie/mlbtv] Fix extraction (#10296)
[yt-dlp.git] / yt_dlp / jsinterp.py
index 1af6ee0aa2b8b568e7ccde91088615cf9c851ef1..a0f32892fd68f6ae8c605b41961cd7ea079aab30 100644 (file)
@@ -9,6 +9,7 @@
 from .utils import (
     NO_DEFAULT,
     ExtractorError,
+    function_with_repr,
     js_to_json,
     remove_quotes,
     truncate_string,
     write_string,
 )
 
-_NAME_RE = r'[a-zA-Z_$][\w$]*'
-_OPERATORS = {  # None => Defined in JSInterpreter._operator
-    '?': None,
 
-    '||': None,
-    '&&': None,
-    '&': operator.and_,
-    '|': operator.or_,
-    '^': operator.xor,
+def _js_bit_op(op):
+    def zeroise(x):
+        if x in (None, JS_Undefined):
+            return 0
+        with contextlib.suppress(TypeError):
+            if math.isnan(x):  # NB: NaN cannot be checked by membership
+                return 0
+        return x
 
-    # FIXME: This should actually be below comparision
-    '>>': operator.rshift,
-    '<<': operator.lshift,
+    def wrapped(a, b):
+        return op(zeroise(a), zeroise(b)) & 0xffffffff
 
-    '<=': operator.le,
-    '>=': operator.ge,
-    '<': operator.lt,
-    '>': operator.gt,
+    return wrapped
 
-    '+': operator.add,
-    '-': operator.sub,
 
-    '*': operator.mul,
-    '/': operator.truediv,
-    '%': operator.mod,
-}
+def _js_arith_op(op):
+
+    def wrapped(a, b):
+        if JS_Undefined in (a, b):
+            return float('nan')
+        return op(a or 0, b or 0)
+
+    return wrapped
+
+
+def _js_div(a, b):
+    if JS_Undefined in (a, b) or not (a or b):
+        return float('nan')
+    return (a or 0) / b if b else float('inf')
+
+
+def _js_mod(a, b):
+    if JS_Undefined in (a, b) or not b:
+        return float('nan')
+    return (a or 0) % b
+
+
+def _js_exp(a, b):
+    if not b:
+        return 1  # even 0 ** 0 !!
+    elif JS_Undefined in (a, b):
+        return float('nan')
+    return (a or 0) ** b
+
+
+def _js_eq_op(op):
+
+    def wrapped(a, b):
+        if {a, b} <= {None, JS_Undefined}:
+            return op(a, a)
+        return op(a, b)
+
+    return wrapped
 
-_MATCHING_PARENS = dict(zip('({[', ')}]'))
-_QUOTES = '\'"'
 
+def _js_comp_op(op):
 
-def _ternary(cndn, if_true=True, if_false=False):
+    def wrapped(a, b):
+        if JS_Undefined in (a, b):
+            return False
+        if isinstance(a, str) or isinstance(b, str):
+            return op(str(a or 0), str(b or 0))
+        return op(a or 0, b or 0)
+
+    return wrapped
+
+
+def _js_ternary(cndn, if_true=True, if_false=False):
     """Simulate JS's ternary operator (cndn?if_true:if_false)"""
-    if cndn in (False, None, 0, ''):
+    if cndn in (False, None, 0, '', JS_Undefined):
         return if_false
     with contextlib.suppress(TypeError):
         if math.isnan(cndn):  # NB: NaN cannot be checked by membership
@@ -57,6 +95,50 @@ def _ternary(cndn, if_true=True, if_false=False):
     return if_true
 
 
+# Ref: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence
+_OPERATORS = {  # None => Defined in JSInterpreter._operator
+    '?': None,
+    '??': None,
+    '||': None,
+    '&&': None,
+
+    '|': _js_bit_op(operator.or_),
+    '^': _js_bit_op(operator.xor),
+    '&': _js_bit_op(operator.and_),
+
+    '===': operator.is_,
+    '!==': operator.is_not,
+    '==': _js_eq_op(operator.eq),
+    '!=': _js_eq_op(operator.ne),
+
+    '<=': _js_comp_op(operator.le),
+    '>=': _js_comp_op(operator.ge),
+    '<': _js_comp_op(operator.lt),
+    '>': _js_comp_op(operator.gt),
+
+    '>>': _js_bit_op(operator.rshift),
+    '<<': _js_bit_op(operator.lshift),
+
+    '+': _js_arith_op(operator.add),
+    '-': _js_arith_op(operator.sub),
+
+    '*': _js_arith_op(operator.mul),
+    '%': _js_mod,
+    '/': _js_div,
+    '**': _js_exp,
+}
+
+_COMP_OPERATORS = {'===', '!==', '==', '!=', '<=', '>=', '<', '>'}
+
+_NAME_RE = r'[a-zA-Z_$][\w$]*'
+_MATCHING_PARENS = dict(zip(*zip('()', '{}', '[]')))
+_QUOTES = '\'"/'
+
+
+class JS_Undefined:
+    pass
+
+
 class JS_Break(ExtractorError):
     def __init__(self):
         ExtractorError.__init__(self, 'Invalid break')
@@ -67,6 +149,12 @@ def __init__(self):
         ExtractorError.__init__(self, 'Invalid continue')
 
 
+class JS_Throw(ExtractorError):
+    def __init__(self, e):
+        self.error = e
+        ExtractorError.__init__(self, f'Uncaught exception {e}')
+
+
 class LocalNameSpace(collections.ChainMap):
     def __setitem__(self, key, value):
         for scope in self.maps:
@@ -81,7 +169,7 @@ def __delitem__(self, key):
 
 class Debugger:
     import sys
-    ENABLED = 'pytest' in sys.modules
+    ENABLED = False and 'pytest' in sys.modules
 
     @staticmethod
     def write(*args, level=100):
@@ -93,9 +181,17 @@ def wrap_interpreter(cls, f):
         def interpret_statement(self, stmt, local_vars, allow_recursion, *args, **kwargs):
             if cls.ENABLED and stmt.strip():
                 cls.write(stmt, level=allow_recursion)
-            ret, should_ret = f(self, stmt, local_vars, allow_recursion, *args, **kwargs)
+            try:
+                ret, should_ret = f(self, stmt, local_vars, allow_recursion, *args, **kwargs)
+            except Exception as e:
+                if cls.ENABLED:
+                    if isinstance(e, ExtractorError):
+                        e = e.orig_msg
+                    cls.write('=> Raises:', e, '<-|', stmt, level=allow_recursion)
+                raise
             if cls.ENABLED and stmt.strip():
-                cls.write(['->', '=>'][should_ret], repr(ret), '<-|', stmt, level=allow_recursion)
+                if should_ret or repr(ret) != stmt:
+                    cls.write(['->', '=>'][should_ret], repr(ret), '<-|', stmt, level=allow_recursion)
             return ret, should_ret
         return interpret_statement
 
@@ -103,11 +199,24 @@ def interpret_statement(self, stmt, local_vars, allow_recursion, *args, **kwargs
 class JSInterpreter:
     __named_object_counter = 0
 
+    _RE_FLAGS = {
+        # special knowledge: Python's re flags are bitmask values, current max 128
+        # invent new bitmask values well above that for literal parsing
+        # TODO: new pattern class to execute matches with these flags
+        'd': 1024,  # Generate indices for substring matches
+        'g': 2048,  # Global search
+        'i': re.I,  # Case-insensitive search
+        'm': re.M,  # Multi-line search
+        's': re.S,  # Allows . to match newline characters
+        'u': re.U,  # Treat a pattern as a sequence of unicode code points
+        'y': 4096,  # Perform a "sticky" search that matches starting at the current position in the target string
+    }
+
     def __init__(self, code, objects=None):
         self.code, self._functions = code, {}
         self._objects = {} if objects is None else objects
 
-    class Exception(ExtractorError):
+    class Exception(ExtractorError):  # noqa: A001
         def __init__(self, msg, expr=None, *args, **kwargs):
             if expr is not None:
                 msg = f'{msg.rstrip()} in: {truncate_string(expr, 50, 50)}'
@@ -116,26 +225,49 @@ def __init__(self, msg, expr=None, *args, **kwargs):
     def _named_object(self, namespace, obj):
         self.__named_object_counter += 1
         name = f'__yt_dlp_jsinterp_obj{self.__named_object_counter}'
+        if callable(obj) and not isinstance(obj, function_with_repr):
+            obj = function_with_repr(obj, f'F<{self.__named_object_counter}>')
         namespace[name] = obj
         return name
 
+    @classmethod
+    def _regex_flags(cls, expr):
+        flags = 0
+        if not expr:
+            return flags, expr
+        for idx, ch in enumerate(expr):  # noqa: B007
+            if ch not in cls._RE_FLAGS:
+                break
+            flags |= cls._RE_FLAGS[ch]
+        return flags, expr[idx + 1:]
+
     @staticmethod
     def _separate(expr, delim=',', max_split=None):
+        OP_CHARS = '+-*/%&|^=<>!,;{}:['
         if not expr:
             return
         counters = {k: 0 for k in _MATCHING_PARENS.values()}
         start, splits, pos, delim_len = 0, 0, 0, len(delim) - 1
-        in_quote, escaping = None, False
+        in_quote, escaping, after_op, in_regex_char_group = None, False, True, False
         for idx, char in enumerate(expr):
             if not in_quote and char in _MATCHING_PARENS:
                 counters[_MATCHING_PARENS[char]] += 1
             elif not in_quote and char in counters:
-                counters[char] -= 1
-            elif not escaping and char in _QUOTES and in_quote in (char, None):
-                in_quote = None if in_quote else char
+                # Something's wrong if we get negative, but ignore it anyway
+                if counters[char]:
+                    counters[char] -= 1
+            elif not escaping:
+                if char in _QUOTES and in_quote in (char, None):
+                    if in_quote or after_op or char != '/':
+                        in_quote = None if in_quote and not in_regex_char_group else char
+                elif in_quote == '/' and char in '[]':
+                    in_regex_char_group = char == '['
             escaping = not escaping and in_quote and char == '\\'
+            in_unary_op = (not in_quote and not in_regex_char_group
+                           and after_op not in (True, False) and char in '-+')
+            after_op = char if (not in_quote and char in OP_CHARS) else (char.isspace() and after_op)
 
-            if char != delim[pos] or any(counters.values()) or in_quote:
+            if char != delim[pos] or any(counters.values()) or in_quote or in_unary_op:
                 pos = 0
                 continue
             elif pos != delim_len:
@@ -149,7 +281,9 @@ def _separate(expr, delim=',', max_split=None):
         yield expr[start:]
 
     @classmethod
-    def _separate_at_paren(cls, expr, delim):
+    def _separate_at_paren(cls, expr, delim=None):
+        if delim is None:
+            delim = expr and _MATCHING_PARENS[expr[0]]
         separated = list(cls._separate(expr, delim, 1))
         if len(separated) < 2:
             raise cls.Exception(f'No terminating paren {delim}', expr)
@@ -157,10 +291,13 @@ def _separate_at_paren(cls, expr, delim):
 
     def _operator(self, op, left_val, right_expr, expr, local_vars, allow_recursion):
         if op in ('||', '&&'):
-            if (op == '&&') ^ _ternary(left_val):
+            if (op == '&&') ^ _js_ternary(left_val):
                 return left_val  # short circuiting
+        elif op == '??':
+            if left_val not in (None, JS_Undefined):
+                return left_val
         elif op == '?':
-            right_expr = _ternary(left_val, *self._separate(right_expr, ':', 1))
+            right_expr = _js_ternary(left_val, *self._separate(right_expr, ':', 1))
 
         right_val = self.interpret_expression(right_expr, local_vars, allow_recursion)
         if not _OPERATORS.get(op):
@@ -171,12 +308,14 @@ def _operator(self, op, left_val, right_expr, expr, local_vars, allow_recursion)
         except Exception as e:
             raise self.Exception(f'Failed to evaluate {left_val!r} {op} {right_val!r}', expr, cause=e)
 
-    def _index(self, obj, idx):
+    def _index(self, obj, idx, allow_undefined=False):
         if idx == 'length':
             return len(obj)
         try:
             return obj[int(idx)] if isinstance(obj, list) else obj[idx]
         except Exception as e:
+            if allow_undefined:
+                return JS_Undefined
             raise self.Exception(f'Cannot get index {idx}', repr(obj), cause=e)
 
     def _dump(self, obj, namespace):
@@ -200,16 +339,25 @@ def interpret_statement(self, stmt, local_vars, allow_recursion=100):
             if should_return:
                 return ret, should_return
 
-        m = re.match(r'(?P<var>var\s)|return(?:\s+|$)', stmt)
+        m = re.match(r'(?P<var>(?:var|const|let)\s)|return(?:\s+|(?=["\'])|$)|(?P<throw>throw\s+)', stmt)
         if m:
             expr = stmt[len(m.group(0)):].strip()
+            if m.group('throw'):
+                raise JS_Throw(self.interpret_expression(expr, local_vars, allow_recursion))
             should_return = not m.group('var')
         if not expr:
             return None, should_return
 
         if expr[0] in _QUOTES:
             inner, outer = self._separate(expr, expr[0], 1)
-            inner = json.loads(js_to_json(f'{inner}{expr[0]}', strict=True))
+            if expr[0] == '/':
+                flags, outer = self._regex_flags(outer)
+                # We don't support regex methods yet, so no point compiling it
+                inner = f'{inner}/{flags}'
+                # Avoid https://github.com/python/cpython/issues/74534
+                # inner = re.compile(inner[1:].replace('[[', r'[\['), flags=flags)
+            else:
+                inner = json.loads(js_to_json(f'{inner}{expr[0]}', strict=True))
             if not outer:
                 return inner, should_return
             expr = self._named_object(local_vars, inner) + outer
@@ -217,16 +365,32 @@ def interpret_statement(self, stmt, local_vars, allow_recursion=100):
         if expr.startswith('new '):
             obj = expr[4:]
             if obj.startswith('Date('):
-                left, right = self._separate_at_paren(obj[4:], ')')
-                expr = unified_timestamp(left[1:-1], False)
-                if not expr:
+                left, right = self._separate_at_paren(obj[4:])
+                date = unified_timestamp(
+                    self.interpret_expression(left, local_vars, allow_recursion), False)
+                if date is None:
                     raise self.Exception(f'Failed to parse date {left!r}', expr)
-                expr = self._dump(int(expr * 1000), local_vars) + right
+                expr = self._dump(int(date * 1000), local_vars) + right
             else:
                 raise self.Exception(f'Unsupported object {obj}', expr)
 
+        if expr.startswith('void '):
+            left = self.interpret_expression(expr[5:], local_vars, allow_recursion)
+            return None, should_return
+
         if expr.startswith('{'):
-            inner, outer = self._separate_at_paren(expr, '}')
+            inner, outer = self._separate_at_paren(expr)
+            # try for object expression (Map)
+            sub_expressions = [list(self._separate(sub_expr.strip(), ':', 1)) for sub_expr in self._separate(inner)]
+            if all(len(sub_expr) == 2 for sub_expr in sub_expressions):
+                def dict_item(key, val):
+                    val = self.interpret_expression(val, local_vars, allow_recursion)
+                    if re.match(_NAME_RE, key):
+                        return key, val
+                    return self.interpret_expression(key, local_vars, allow_recursion), val
+
+                return dict(dict_item(k, v) for k, v in sub_expressions), should_return
+
             inner, should_abort = self.interpret_statement(inner, local_vars, allow_recursion)
             if not outer or should_abort:
                 return inner, should_abort or should_return
@@ -234,7 +398,7 @@ def interpret_statement(self, stmt, local_vars, allow_recursion=100):
                 expr = self._dump(inner, local_vars) + outer
 
         if expr.startswith('('):
-            inner, outer = self._separate_at_paren(expr, ')')
+            inner, outer = self._separate_at_paren(expr)
             inner, should_abort = self.interpret_statement(inner, local_vars, allow_recursion)
             if not outer or should_abort:
                 return inner, should_abort or should_return
@@ -242,38 +406,77 @@ def interpret_statement(self, stmt, local_vars, allow_recursion=100):
                 expr = self._dump(inner, local_vars) + outer
 
         if expr.startswith('['):
-            inner, outer = self._separate_at_paren(expr, ']')
+            inner, outer = self._separate_at_paren(expr)
             name = self._named_object(local_vars, [
                 self.interpret_expression(item, local_vars, allow_recursion)
                 for item in self._separate(inner)])
             expr = name + outer
 
-        m = re.match(r'(?P<try>try|finally)\s*|(?:(?P<catch>catch)|(?P<for>for)|(?P<switch>switch))\s*\(', expr)
-        if m and m.group('try'):
-            if expr[m.end()] == '{':
-                try_expr, expr = self._separate_at_paren(expr[m.end():], '}')
-            else:
-                try_expr, expr = expr[m.end() - 1:], ''
-            ret, should_abort = self.interpret_statement(try_expr, local_vars, allow_recursion)
+        m = re.match(r'''(?x)
+                (?P<try>try)\s*\{|
+                (?P<if>if)\s*\(|
+                (?P<switch>switch)\s*\(|
+                (?P<for>for)\s*\(
+                ''', expr)
+        md = m.groupdict() if m else {}
+        if md.get('if'):
+            cndn, expr = self._separate_at_paren(expr[m.end() - 1:])
+            if_expr, expr = self._separate_at_paren(expr.lstrip())
+            # TODO: "else if" is not handled
+            else_expr = None
+            m = re.match(r'else\s*{', expr)
+            if m:
+                else_expr, expr = self._separate_at_paren(expr[m.end() - 1:])
+            cndn = _js_ternary(self.interpret_expression(cndn, local_vars, allow_recursion))
+            ret, should_abort = self.interpret_statement(
+                if_expr if cndn else else_expr, local_vars, allow_recursion)
             if should_abort:
                 return ret, True
-            ret, should_abort = self.interpret_statement(expr, local_vars, allow_recursion)
-            return ret, should_abort or should_return
 
-        elif m and m.group('catch'):
-            # We ignore the catch block
-            _, expr = self._separate_at_paren(expr, '}')
-            ret, should_abort = self.interpret_statement(expr, local_vars, allow_recursion)
-            return ret, should_abort or should_return
+        if md.get('try'):
+            try_expr, expr = self._separate_at_paren(expr[m.end() - 1:])
+            err = None
+            try:
+                ret, should_abort = self.interpret_statement(try_expr, local_vars, allow_recursion)
+                if should_abort:
+                    return ret, True
+            except Exception as e:
+                # XXX: This works for now, but makes debugging future issues very hard
+                err = e
+
+            pending = (None, False)
+            m = re.match(fr'catch\s*(?P<err>\(\s*{_NAME_RE}\s*\))?\{{', expr)
+            if m:
+                sub_expr, expr = self._separate_at_paren(expr[m.end() - 1:])
+                if err:
+                    catch_vars = {}
+                    if m.group('err'):
+                        catch_vars[m.group('err')] = err.error if isinstance(err, JS_Throw) else err
+                    catch_vars = local_vars.new_child(catch_vars)
+                    err, pending = None, self.interpret_statement(sub_expr, catch_vars, allow_recursion)
+
+            m = re.match(r'finally\s*\{', expr)
+            if m:
+                sub_expr, expr = self._separate_at_paren(expr[m.end() - 1:])
+                ret, should_abort = self.interpret_statement(sub_expr, local_vars, allow_recursion)
+                if should_abort:
+                    return ret, True
+
+            ret, should_abort = pending
+            if should_abort:
+                return ret, True
 
-        elif m and m.group('for'):
-            constructor, remaining = self._separate_at_paren(expr[m.end() - 1:], ')')
+            if err:
+                raise err
+
+        elif md.get('for'):
+            constructor, remaining = self._separate_at_paren(expr[m.end() - 1:])
             if remaining.startswith('{'):
-                body, expr = self._separate_at_paren(remaining, '}')
+                body, expr = self._separate_at_paren(remaining)
             else:
-                switch_m = re.match(r'switch\s*\(', remaining)  # FIXME
+                switch_m = re.match(r'switch\s*\(', remaining)  # FIXME: ?
                 if switch_m:
-                    switch_val, remaining = self._separate_at_paren(remaining[switch_m.end() - 1:], ')')
+                    switch_val, remaining = self._separate_at_paren(remaining[switch_m.end() - 1:])
                     body, expr = self._separate_at_paren(remaining, '}')
                     body = 'switch(%s){%s}' % (switch_val, body)
                 else:
@@ -281,7 +484,7 @@ def interpret_statement(self, stmt, local_vars, allow_recursion=100):
             start, cndn, increment = self._separate(constructor, ';')
             self.interpret_expression(start, local_vars, allow_recursion)
             while True:
-                if not _ternary(self.interpret_expression(cndn, local_vars, allow_recursion)):
+                if not _js_ternary(self.interpret_expression(cndn, local_vars, allow_recursion)):
                     break
                 try:
                     ret, should_abort = self.interpret_statement(body, local_vars, allow_recursion)
@@ -292,11 +495,9 @@ def interpret_statement(self, stmt, local_vars, allow_recursion=100):
                 except JS_Continue:
                     pass
                 self.interpret_expression(increment, local_vars, allow_recursion)
-            ret, should_abort = self.interpret_statement(expr, local_vars, allow_recursion)
-            return ret, should_abort or should_return
 
-        elif m and m.group('switch'):
-            switch_val, remaining = self._separate_at_paren(expr[m.end() - 1:], ')')
+        elif md.get('switch'):
+            switch_val, remaining = self._separate_at_paren(expr[m.end() - 1:])
             switch_val = self.interpret_expression(switch_val, local_vars, allow_recursion)
             body, expr = self._separate_at_paren(remaining, '}')
             items = body.replace('default:', 'case default:').split('case ')[1:]
@@ -307,7 +508,8 @@ def interpret_statement(self, stmt, local_vars, allow_recursion=100):
                     if default:
                         matched = matched or case == 'default'
                     elif not matched:
-                        matched = case != 'default' and switch_val == self.interpret_expression(case, local_vars, allow_recursion)
+                        matched = (case != 'default'
+                                   and switch_val == self.interpret_expression(case, local_vars, allow_recursion))
                     if not matched:
                         continue
                     try:
@@ -318,16 +520,19 @@ def interpret_statement(self, stmt, local_vars, allow_recursion=100):
                         break
                 if matched:
                     break
+
+        if md:
             ret, should_abort = self.interpret_statement(expr, local_vars, allow_recursion)
             return ret, should_abort or should_return
 
         # Comma separated statements
         sub_expressions = list(self._separate(expr))
-        expr = sub_expressions.pop().strip() if sub_expressions else ''
-        for sub_expr in sub_expressions:
-            ret, should_abort = self.interpret_statement(sub_expr, local_vars, allow_recursion)
-            if should_abort:
-                return ret, True
+        if len(sub_expressions) > 1:
+            for sub_expr in sub_expressions:
+                ret, should_abort = self.interpret_statement(sub_expr, local_vars, allow_recursion)
+                if should_abort:
+                    return ret, True
+            return ret, False
 
         for m in re.finditer(rf'''(?x)
                 (?P<pre_sign>\+\+|--)(?P<var1>{_NAME_RE})|
@@ -347,14 +552,14 @@ def interpret_statement(self, stmt, local_vars, allow_recursion=100):
         m = re.match(fr'''(?x)
             (?P<assign>
                 (?P<out>{_NAME_RE})(?:\[(?P<index>[^\]]+?)\])?\s*
-                (?P<op>{"|".join(map(re.escape, _OPERATORS))})?
-                =(?P<expr>.*)$
+                (?P<op>{"|".join(map(re.escape, set(_OPERATORS) - _COMP_OPERATORS))})?
+                =(?!=)(?P<expr>.*)$
             )|(?P<return>
-                (?!if|return|true|false|null|undefined)(?P<name>{_NAME_RE})$
+                (?!if|return|true|false|null|undefined|NaN)(?P<name>{_NAME_RE})$
             )|(?P<indexing>
                 (?P<in>{_NAME_RE})\[(?P<idx>.+)\]$
             )|(?P<attribute>
-                (?P<var>{_NAME_RE})(?:\.(?P<member>[^(]+)|\[(?P<member2>[^\]]+)\])\s*
+                (?P<var>{_NAME_RE})(?:(?P<nullish>\?)?\.(?P<member>[^(]+)|\[(?P<member2>[^\]]+)\])\s*
             )|(?P<function>
                 (?P<fname>{_NAME_RE})\((?P<args>.*)\)$
             )''', expr)
@@ -365,7 +570,7 @@ def interpret_statement(self, stmt, local_vars, allow_recursion=100):
                 local_vars[m.group('out')] = self._operator(
                     m.group('op'), left_val, m.group('expr'), expr, local_vars, allow_recursion)
                 return local_vars[m.group('out')], should_return
-            elif left_val is None:
+            elif left_val in (None, JS_Undefined):
                 raise self.Exception(f'Cannot index undefined variable {m.group("out")}', expr)
 
             idx = self.interpret_expression(m.group('index'), local_vars, allow_recursion)
@@ -373,19 +578,23 @@ def interpret_statement(self, stmt, local_vars, allow_recursion=100):
                 raise self.Exception(f'List index {idx} must be integer', expr)
             idx = int(idx)
             left_val[idx] = self._operator(
-                m.group('op'), left_val[idx], m.group('expr'), expr, local_vars, allow_recursion)
+                m.group('op'), self._index(left_val, idx), m.group('expr'), expr, local_vars, allow_recursion)
             return left_val[idx], should_return
 
         elif expr.isdigit():
             return int(expr), should_return
 
         elif expr == 'break':
-            raise JS_Break()
+            raise JS_Break
         elif expr == 'continue':
-            raise JS_Continue()
+            raise JS_Continue
+        elif expr == 'undefined':
+            return JS_Undefined, should_return
+        elif expr == 'NaN':
+            return float('NaN'), should_return
 
         elif m and m.group('return'):
-            return local_vars[m.group('name')], should_return
+            return local_vars.get(m.group('name'), JS_Undefined), should_return
 
         with contextlib.suppress(ValueError):
             return json.loads(js_to_json(expr, strict=True)), should_return
@@ -397,24 +606,27 @@ def interpret_statement(self, stmt, local_vars, allow_recursion=100):
 
         for op in _OPERATORS:
             separated = list(self._separate(expr, op))
-            if len(separated) < 2:
-                continue
             right_expr = separated.pop()
-            while op == '-' and len(separated) > 1 and not separated[-1].strip():
-                right_expr = f'-{right_expr}'
-                separated.pop()
+            while True:
+                if op in '?<>*-' and len(separated) > 1 and not separated[-1].strip():
+                    separated.pop()
+                elif not (separated and op == '?' and right_expr.startswith('.')):
+                    break
+                right_expr = f'{op}{right_expr}'
+                if op != '-':
+                    right_expr = f'{separated.pop()}{op}{right_expr}'
+            if not separated:
+                continue
             left_val = self.interpret_expression(op.join(separated), local_vars, allow_recursion)
-            return self._operator(op, 0 if left_val is None else left_val,
-                                  right_expr, expr, local_vars, allow_recursion), should_return
+            return self._operator(op, left_val, right_expr, expr, local_vars, allow_recursion), should_return
 
         if m and m.group('attribute'):
-            variable = m.group('var')
-            member = m.group('member')
+            variable, member, nullish = m.group('var', 'member', 'nullish')
             if not member:
                 member = self.interpret_expression(m.group('member2'), local_vars, allow_recursion)
             arg_str = expr[m.end():]
             if arg_str.startswith('('):
-                arg_str, remaining = self._separate_at_paren(arg_str, ')')
+                arg_str, remaining = self._separate_at_paren(arg_str)
             else:
                 arg_str, remaining = None, arg_str
 
@@ -436,24 +648,31 @@ def eval_method():
                 obj = local_vars.get(variable, types.get(variable, NO_DEFAULT))
                 if obj is NO_DEFAULT:
                     if variable not in self._objects:
-                        self._objects[variable] = self.extract_object(variable)
-                    obj = self._objects[variable]
+                        try:
+                            self._objects[variable] = self.extract_object(variable)
+                        except self.Exception:
+                            if not nullish:
+                                raise
+                    obj = self._objects.get(variable, JS_Undefined)
+
+                if nullish and obj is JS_Undefined:
+                    return JS_Undefined
 
                 # Member access
                 if arg_str is None:
-                    return self._index(obj, member)
+                    return self._index(obj, member, nullish)
 
                 # Function call
                 argvals = [
                     self.interpret_expression(v, local_vars, allow_recursion)
                     for v in self._separate(arg_str)]
 
-                if obj == str:
+                if obj is str:
                     if member == 'fromCharCode':
                         assertion(argvals, 'takes one or more arguments')
                         return ''.join(map(chr, argvals))
                     raise self.Exception(f'Unsupported String method {member}', expr)
-                elif obj == float:
+                elif obj is float:
                     if member == 'pow':
                         assertion(len(argvals) == 2, 'takes two arguments')
                         return argvals[0] ** argvals[1]
@@ -478,12 +697,12 @@ def eval_method():
                 elif member == 'splice':
                     assertion(isinstance(obj, list), 'must be applied on a list')
                     assertion(argvals, 'takes one or more arguments')
-                    index, howMany = map(int, (argvals + [len(obj)])[:2])
+                    index, how_many = map(int, ([*argvals, len(obj)])[:2])
                     if index < 0:
                         index += len(obj)
                     add_items = argvals[2:]
                     res = []
-                    for i in range(index, min(index + howMany, len(obj))):
+                    for _ in range(index, min(index + how_many, len(obj))):
                         res.append(obj.pop(index))
                     for i, item in enumerate(add_items):
                         obj.insert(index + i, item)
@@ -507,16 +726,23 @@ def eval_method():
                 elif member == 'forEach':
                     assertion(argvals, 'takes one or more arguments')
                     assertion(len(argvals) <= 2, 'takes at-most 2 arguments')
-                    f, this = (argvals + [''])[:2]
+                    f, this = ([*argvals, ''])[:2]
                     return [f((item, idx, obj), {'this': this}, allow_recursion) for idx, item in enumerate(obj)]
                 elif member == 'indexOf':
                     assertion(argvals, 'takes one or more arguments')
                     assertion(len(argvals) <= 2, 'takes at-most 2 arguments')
-                    idx, start = (argvals + [0])[:2]
+                    idx, start = ([*argvals, 0])[:2]
                     try:
                         return obj.index(idx, start)
                     except ValueError:
                         return -1
+                elif member == 'charCodeAt':
+                    assertion(isinstance(obj, str), 'must be applied on a string')
+                    assertion(len(argvals) == 1, 'takes exactly one argument')
+                    idx = argvals[0] if isinstance(argvals[0], int) else 0
+                    if idx >= len(obj):
+                        return None
+                    return ord(obj[idx])
 
                 idx = int(member) if isinstance(obj, list) else member
                 return obj[idx](argvals, allow_recursion=allow_recursion)
@@ -553,7 +779,7 @@ def extract_object(self, objname):
         obj = {}
         obj_m = re.search(
             r'''(?x)
-                (?<!this\.)%s\s*=\s*{\s*
+                (?<!\.)%s\s*=\s*{\s*
                     (?P<fields>(%s\s*:\s*function\s*\(.*?\)\s*{.*?}(?:,\s*)?)*)
                 }\s*;
             ''' % (re.escape(objname), _FUNC_NAME_RE),
@@ -564,12 +790,13 @@ def extract_object(self, objname):
         # Currently, it only supports function definitions
         fields_m = re.finditer(
             r'''(?x)
-                (?P<key>%s)\s*:\s*function\s*\((?P<args>[a-z,]+)\){(?P<code>[^}]+)}
-            ''' % _FUNC_NAME_RE,
+                (?P<key>%s)\s*:\s*function\s*\((?P<args>(?:%s|,)*)\){(?P<code>[^}]+)}
+            ''' % (_FUNC_NAME_RE, _NAME_RE),
             fields)
         for f in fields_m:
             argnames = f.group('args').split(',')
-            obj[remove_quotes(f.group('key'))] = self.build_function(argnames, f.group('code'))
+            name = remove_quotes(f.group('key'))
+            obj[name] = function_with_repr(self.build_function(argnames, f.group('code')), f'F<{name}>')
 
         return obj
 
@@ -580,18 +807,20 @@ def extract_function_code(self, funcname):
                 (?:
                     function\s+%(name)s|
                     [{;,]\s*%(name)s\s*=\s*function|
-                    var\s+%(name)s\s*=\s*function
+                    (?:var|const|let)\s+%(name)s\s*=\s*function
                 )\s*
                 \((?P<args>[^)]*)\)\s*
                 (?P<code>{.+})''' % {'name': re.escape(funcname)},
             self.code)
-        code, _ = self._separate_at_paren(func_m.group('code'), '}')
         if func_m is None:
             raise self.Exception(f'Could not find JS function "{funcname}"')
+        code, _ = self._separate_at_paren(func_m.group('code'))
         return [x.strip() for x in func_m.group('args').split(',')], code
 
     def extract_function(self, funcname):
-        return self.extract_function_from_code(*self.extract_function_code(funcname))
+        return function_with_repr(
+            self.extract_function_from_code(*self.extract_function_code(funcname)),
+            f'F<{funcname}>')
 
     def extract_function_from_code(self, argnames, code, *global_stack):
         local_vars = {}
@@ -600,7 +829,7 @@ def extract_function_from_code(self, argnames, code, *global_stack):
             if mobj is None:
                 break
             start, body_start = mobj.span()
-            body, remaining = self._separate_at_paren(code[body_start - 1:], '}')
+            body, remaining = self._separate_at_paren(code[body_start - 1:])
             name = self._named_object(local_vars, self.extract_function_from_code(
                 [x.strip() for x in mobj.group('args').split(',')],
                 body, local_vars, *global_stack))
@@ -615,12 +844,10 @@ def build_function(self, argnames, code, *global_stack):
         argnames = tuple(argnames)
 
         def resf(args, kwargs={}, allow_recursion=100):
-            global_stack[0].update({
-                **dict(itertools.zip_longest(argnames, args, fillvalue=None)),
-                **kwargs
-            })
+            global_stack[0].update(itertools.zip_longest(argnames, args, fillvalue=None))
+            global_stack[0].update(kwargs)
             var_stack = LocalNameSpace(*global_stack)
-            ret, should_abort = self.interpret_statement(code.replace('\n', ''), var_stack, allow_recursion - 1)
+            ret, should_abort = self.interpret_statement(code.replace('\n', ' '), var_stack, allow_recursion - 1)
             if should_abort:
                 return ret
         return resf