diff --git a/test/js2tests/__init__.py b/test/js2tests/__init__.py
index a9b1660b8..05df89c4f 100644
--- a/test/js2tests/__init__.py
+++ b/test/js2tests/__init__.py
@@ -1,3 +1,5 @@
+# TODO use json instead of py
+# TODO create devscript to generate ASTs (using e.g. acorn)
 # """
 # This package contains templates for `test_jsinterp` and `test_interp_parse` to create test methods.
 # These modules will create a test method for each module in this package. A test method consist of one or more subtest.
diff --git a/test/js2tests/call.py b/test/js2tests/call.py
index e49d56e15..f08f96a80 100644
--- a/test/js2tests/call.py
+++ b/test/js2tests/call.py
@@ -39,7 +39,7 @@ tests = [
             ])
         ]
     }, {
-        # FIXME built-in functions not yet implemented
+        # FIXME built-in functions are not yet implemented
         'exclude': ('jsinterp2',),
         'code': 'function x(a) { return a.split(""); }',
         'asserts': [{'value': ["a", "b", "c"], 'call': ('x', "abc")}],
diff --git a/youtube_dl/jsinterp2/jsbuilt_ins/internals.py b/youtube_dl/jsinterp2/jsbuilt_ins/internals.py
index e822d87fc..3e888b4ab 100644
--- a/youtube_dl/jsinterp2/jsbuilt_ins/internals.py
+++ b/youtube_dl/jsinterp2/jsbuilt_ins/internals.py
@@ -83,6 +83,7 @@ def to_number(o):
             if v:
                 s = 1 if v.startswith('+') or v.startswith('-') else 0
                 if v[s:] == 'Infinity':
+                    # FIXME: declare in jsbuilt_ins (propery of global_obj)
                     return float(v[:s] + 'inf')  # 10 ** 10000 according to spec
                 elif v[s:].isdigit():
                     return int(v)
@@ -93,6 +94,7 @@ def to_number(o):
             else:
                 return 0
         else:
+            # FIXME: declare in jsbuilt_ins (propery of global_obj)
             return float('nan')
 
     elif isinstance(o, JSObjectPrototype):
diff --git a/youtube_dl/jsinterp2/jsgrammar.py b/youtube_dl/jsinterp2/jsgrammar.py
index 44bf15603..4b2e228c0 100644
--- a/youtube_dl/jsinterp2/jsgrammar.py
+++ b/youtube_dl/jsinterp2/jsgrammar.py
@@ -30,7 +30,7 @@ __ESC_HEX_RE = r'x[0-9a-fA-F]{2}'
 
 
 # NOTE order is fixed due to regex matching, does not represent any precedence
-# NOTE unary operator 'delete', 'void', 'instanceof' and relation 'in' and 'instanceof' do not handled this way
+# NOTE unary operator 'delete', 'void', 'instanceof' and relation 'in' and 'instanceof' are not handled this way
 _logical_operator = ['||', '&&']
 _relation = ['===', '!==', '==', '!=', '<=', '>=', '<', '>']
 _unary_operator = ['++', '--', '!', '~']
@@ -44,8 +44,8 @@ _NAME_RE = r'[a-zA-Z_$][a-zA-Z_$0-9]*'
 
 # non-escape char also can be escaped, but line continuation and quotes has to be
 # XXX unicode and hexadecimal escape sequences should be validated
-_SINGLE_QUOTED_RE = r"""'(?:(?:\\'|\n)|[^'\n])*'"""
-_DOUBLE_QUOTED_RE = r'''"(?:(?:\\"|\n)|[^"\n])*"'''
+_SINGLE_QUOTED_RE = r"'(?:(?:\\'|\n)|[^'\n])*'"
+_DOUBLE_QUOTED_RE = r'"(?:(?:\\"|\n)|[^"\n])*"'
 _STRING_RE = r'(?:%s)|(?:%s)' % (_SINGLE_QUOTED_RE, _DOUBLE_QUOTED_RE)
 
 _INTEGER_RE = r'(?:%(hex)s)|(?:%(dec)s)|(?:%(oct)s)' % {'hex': __HEXADECIMAL_RE, 'dec': __DECIMAL_RE, 'oct': __OCTAL_RE}
@@ -54,7 +54,7 @@ _FLOAT_RE = r'(?:(?:%(dec)s\.[0-9]*)|(?:\.[0-9]+))(?:[eE][+-]?[0-9]+)?' % {'dec'
 _BOOL_RE = r'true|false'
 _NULL_RE = r'null'
 
-# XXX early validation might needed
+# XXX early validation might be needed
 # r'''/(?!\*)
 #     (?:(?:\\(?:[tnvfr0.\\+*?^$\[\]{}()|/]|[0-7]{3}|x[0-9A-Fa-f]{2}|u[0-9A-Fa-f]{4}|c[A-Z]|))|[^/\n])*
 #     /(?:(?![gimy]*(?P<flag>[gimy])[gimy]*(?P=flag))[gimy]{0,4}\b|\s|$)'''