LibJS: Lex and parse regex literals, add RegExp objects

This adds regex parsing/lexing, as well as a relatively empty
RegExpObject. The purpose of this patch is to allow the engine to not
get hung up on parsing regexes. This will aid in finding new syntax
errors (say, from google or twitter) without having to replace all of
their regexes first!

18 files changed, 413 insertions, 5 deletions

diff --git a/Libraries/LibJS/AST.cpp b/Libraries/LibJS/AST.cpp
index 840b29412d..2f12a49e36 100644
--- a/Libraries/LibJS/AST.cpp
+++ b/Libraries/LibJS/AST.cpp
@@ -39,6 +39,7 @@
 #include <LibJS/Runtime/NativeFunction.h>
 #include <LibJS/Runtime/PrimitiveString.h>
 #include <LibJS/Runtime/Reference.h>
+#include <LibJS/Runtime/RegExpObject.h>
 #include <LibJS/Runtime/ScriptFunction.h>
 #include <LibJS/Runtime/Shape.h>
 #include <LibJS/Runtime/StringObject.h>
@@ -1429,6 +1430,17 @@ Value NullLiteral::execute(Interpreter&) const
     return js_null();
 }
 
+void RegExpLiteral::dump(int indent) const
+{
+    print_indent(indent);
+    printf("%s (/%s/%s)\n", class_name(), content().characters(), flags().characters());
+}
+
+Value RegExpLiteral::execute(Interpreter& interpreter) const
+{
+    return RegExpObject::create(interpreter.global_object(), content(), flags());
+}
+
 void ArrayExpression::dump(int indent) const
 {
     ASTNode::dump(indent);
diff --git a/Libraries/LibJS/AST.h b/Libraries/LibJS/AST.h
index 82b6cf979e..72f8972cc3 100644
--- a/Libraries/LibJS/AST.h
+++ b/Libraries/LibJS/AST.h
@@ -585,6 +585,27 @@ private:
     virtual const char* class_name() const override { return "NullLiteral"; }
 };
 
+class RegExpLiteral final : public Literal {
+public:
+    explicit RegExpLiteral(String content, String flags)
+        : m_content(content)
+        , m_flags(flags)
+    {
+    }
+
+    virtual Value execute(Interpreter&) const override;
+    virtual void dump(int indent) const override;
+
+    const String& content() const { return m_content; }
+    const String& flags() const { return m_flags; }
+
+private:
+    virtual const char* class_name() const override { return "RegexLiteral"; }
+
+    String m_content;
+    String m_flags;
+};
+
 class Identifier final : public Expression {
 public:
     explicit Identifier(const FlyString& string)
diff --git a/Libraries/LibJS/CMakeLists.txt b/Libraries/LibJS/CMakeLists.txt
index 38f84aee58..c170fe908a 100644
--- a/Libraries/LibJS/CMakeLists.txt
+++ b/Libraries/LibJS/CMakeLists.txt
@@ -47,6 +47,9 @@ set(SOURCES
     Runtime/ProxyPrototype.cpp
     Runtime/Reference.cpp
     Runtime/ReflectObject.cpp
+    Runtime/RegExpConstructor.cpp
+    Runtime/RegExpObject.cpp
+    Runtime/RegExpPrototype.cpp
     Runtime/ScriptFunction.cpp
     Runtime/Shape.cpp
     Runtime/StringConstructor.cpp
diff --git a/Libraries/LibJS/Forward.h b/Libraries/LibJS/Forward.h
index 68fd24cad3..17c7953221 100644
--- a/Libraries/LibJS/Forward.h
+++ b/Libraries/LibJS/Forward.h
@@ -35,6 +35,7 @@
     __JS_ENUMERATE(NumberObject, number, NumberPrototype, NumberConstructor)     \
     __JS_ENUMERATE(Object, object, ObjectPrototype, ObjectConstructor)           \
     __JS_ENUMERATE(ProxyObject, proxy, ProxyPrototype, ProxyConstructor)         \
+    __JS_ENUMERATE(RegExpObject, regexp, RegExpPrototype, RegExpConstructor)     \
     __JS_ENUMERATE(StringObject, string, StringPrototype, StringConstructor)     \
     __JS_ENUMERATE(SymbolObject, symbol, SymbolPrototype, SymbolConstructor)
 
diff --git a/Libraries/LibJS/Lexer.cpp b/Libraries/LibJS/Lexer.cpp
index f67d8ff9bb..597e48c187 100644
--- a/Libraries/LibJS/Lexer.cpp
+++ b/Libraries/LibJS/Lexer.cpp
@@ -244,6 +244,22 @@ bool Lexer::is_numeric_literal_start() const
     return isdigit(m_current_char) || (m_current_char == '.' && m_position < m_source.length() && isdigit(m_source[m_position]));
 }
 
+bool Lexer::slash_means_division() const
+{
+    auto type = m_current_token.type();
+    return type == TokenType::BoolLiteral
+           || type == TokenType::BracketClose
+           || type == TokenType::CurlyClose
+           || type == TokenType::Identifier
+           || type == TokenType::NullLiteral
+           || type == TokenType::NumericLiteral
+           || type == TokenType::ParenClose
+           || type == TokenType::RegexLiteral
+           || type == TokenType::StringLiteral
+           || type == TokenType::TemplateLiteralEnd
+           || type == TokenType::This;
+}
+
 Token Lexer::next()
 {
     size_t trivia_start = m_position;
@@ -277,7 +293,11 @@ Token Lexer::next()
     size_t value_start = m_position;
     auto token_type = TokenType::Invalid;
 
-    if (m_current_char == '`') {
+    if (m_current_token.type() == TokenType::RegexLiteral && !is_eof() && isalpha(m_current_char)) {
+        token_type = TokenType::RegexFlags;
+        while (!is_eof() && isalpha(m_current_char))
+            consume();
+    } else if (m_current_char == '`') {
         consume();
 
         if (!in_template) {
@@ -452,6 +472,28 @@ Token Lexer::next()
         if (!found_four_char_token && !found_three_char_token && !found_two_char_token && !found_one_char_token) {
             consume();
             token_type = TokenType::Invalid;
+        } else if (token_type == TokenType::Slash && !slash_means_division()) {
+            token_type = TokenType::RegexLiteral;
+
+            while (!is_eof()) {
+                if (m_current_char == '[') {
+                    m_regex_is_in_character_class = true;
+                } else if (m_current_char == ']') {
+                    m_regex_is_in_character_class = false;
+                } else if (!m_regex_is_in_character_class && m_current_char == '/') {
+                    break;
+                }
+
+                if (match('\\', '/') || match('\\', '[') || (m_regex_is_in_character_class && match('\\', ']')))
+                    consume();
+                consume();
+            }
+
+            if (is_eof()) {
+                token_type = TokenType::UnterminatedRegexLiteral;
+            } else {
+                consume();
+            }
         }
     }
 
diff --git a/Libraries/LibJS/Lexer.h b/Libraries/LibJS/Lexer.h
index 71f22b0535..18f9bfb2d3 100644
--- a/Libraries/LibJS/Lexer.h
+++ b/Libraries/LibJS/Lexer.h
@@ -53,6 +53,7 @@ private:
     bool match(char, char) const;
     bool match(char, char, char) const;
     bool match(char, char, char, char) const;
+    bool slash_means_division() const;
 
     StringView m_source;
     size_t m_position { 0 };
@@ -61,6 +62,8 @@ private:
     size_t m_line_number { 1 };
     size_t m_line_column { 0 };
 
+    bool m_regex_is_in_character_class { false };
+
     struct TemplateState {
         bool in_expr;
         u8 open_bracket_count;
diff --git a/Libraries/LibJS/MarkupGenerator.cpp b/Libraries/LibJS/MarkupGenerator.cpp
index 6efaf65855..8836c7b069 100644
--- a/Libraries/LibJS/MarkupGenerator.cpp
+++ b/Libraries/LibJS/MarkupGenerator.cpp
@@ -223,6 +223,7 @@ MarkupGenerator::StyleType MarkupGenerator::style_type_for_token(Token token)
     case TokenType::TemplateLiteralEnd:
     case TokenType::TemplateLiteralString:
     case TokenType::RegexLiteral:
+    case TokenType::RegexFlags:
     case TokenType::UnterminatedStringLiteral:
         return StyleType::String;
     case TokenType::BracketClose:
diff --git a/Libraries/LibJS/Parser.cpp b/Libraries/LibJS/Parser.cpp
index 1739c7c2b8..d21b0171c2 100644
--- a/Libraries/LibJS/Parser.cpp
+++ b/Libraries/LibJS/Parser.cpp
@@ -464,6 +464,8 @@ NonnullRefPtr<Expression> Parser::parse_primary_expression()
         return parse_function_node<FunctionExpression>();
     case TokenType::BracketOpen:
         return parse_array_expression();
+    case TokenType::RegexLiteral:
+        return parse_regexp_literal();
     case TokenType::TemplateLiteralStart:
         return parse_template_literal(false);
     case TokenType::New:
@@ -475,6 +477,13 @@ NonnullRefPtr<Expression> Parser::parse_primary_expression()
     }
 }
 
+NonnullRefPtr<RegExpLiteral> Parser::parse_regexp_literal()
+{
+    auto content = consume().value();
+    auto flags = match(TokenType::RegexFlags) ? consume().value() : "";
+    return create_ast_node<RegExpLiteral>(content.substring_view(1, content.length() - 2), flags);
+}
+
 NonnullRefPtr<Expression> Parser::parse_unary_prefixed_expression()
 {
     auto precedence = operator_precedence(m_parser_state.m_current_token.type());
@@ -1449,6 +1458,7 @@ bool Parser::match_expression() const
         || type == TokenType::ParenOpen
         || type == TokenType::Function
         || type == TokenType::This
+        || type == TokenType::RegexLiteral
         || match_unary_prefixed_expression();
 }
 
diff --git a/Libraries/LibJS/Parser.h b/Libraries/LibJS/Parser.h
index 4d36d85f98..0b256d3f76 100644
--- a/Libraries/LibJS/Parser.h
+++ b/Libraries/LibJS/Parser.h
@@ -70,6 +70,7 @@ public:
     NonnullRefPtr<Expression> parse_expression(int min_precedence, Associativity associate = Associativity::Right, Vector<TokenType> forbidden = {});
     NonnullRefPtr<Expression> parse_primary_expression();
     NonnullRefPtr<Expression> parse_unary_prefixed_expression();
+    NonnullRefPtr<RegExpLiteral> parse_regexp_literal();
     NonnullRefPtr<ObjectExpression> parse_object_expression();
     NonnullRefPtr<ArrayExpression> parse_array_expression();
     NonnullRefPtr<StringLiteral> parse_string_literal(Token token);
diff --git a/Libraries/LibJS/Runtime/GlobalObject.cpp b/Libraries/LibJS/Runtime/GlobalObject.cpp
index 2032178256..f3aebccb0e 100644
--- a/Libraries/LibJS/Runtime/GlobalObject.cpp
+++ b/Libraries/LibJS/Runtime/GlobalObject.cpp
@@ -26,8 +26,6 @@
  */
 
 #include <AK/LogStream.h>
-#include <AK/String.h>
-#include <LibJS/Heap/Heap.h>
 #include <LibJS/Interpreter.h>
 #include <LibJS/Runtime/ArrayConstructor.h>
 #include <LibJS/Runtime/ArrayPrototype.h>
@@ -36,13 +34,11 @@
 #include <LibJS/Runtime/ConsoleObject.h>
 #include <LibJS/Runtime/DateConstructor.h>
 #include <LibJS/Runtime/DatePrototype.h>
-#include <LibJS/Runtime/Error.h>
 #include <LibJS/Runtime/ErrorConstructor.h>
 #include <LibJS/Runtime/ErrorPrototype.h>
 #include <LibJS/Runtime/FunctionConstructor.h>
 #include <LibJS/Runtime/FunctionPrototype.h>
 #include <LibJS/Runtime/GlobalObject.h>
-#include <LibJS/Runtime/LexicalEnvironment.h>
 #include <LibJS/Runtime/MathObject.h>
 #include <LibJS/Runtime/NativeFunction.h>
 #include <LibJS/Runtime/NumberConstructor.h>
@@ -53,6 +49,8 @@
 #include <LibJS/Runtime/ProxyConstructor.h>
 #include <LibJS/Runtime/ProxyPrototype.h>
 #include <LibJS/Runtime/ReflectObject.h>
+#include <LibJS/Runtime/RegExpConstructor.h>
+#include <LibJS/Runtime/RegExpPrototype.h>
 #include <LibJS/Runtime/Shape.h>
 #include <LibJS/Runtime/StringConstructor.h>
 #include <LibJS/Runtime/StringPrototype.h>
@@ -106,6 +104,7 @@ void GlobalObject::initialize()
     add_constructor("Number", m_number_constructor, *m_number_prototype);
     add_constructor("Object", m_object_constructor, *m_object_prototype);
     add_constructor("Proxy", m_proxy_constructor, *m_proxy_prototype);
+    add_constructor("RegExp", m_regexp_constructor, *m_regexp_prototype);
     add_constructor("String", m_string_constructor, *m_string_prototype);
     add_constructor("Symbol", m_symbol_constructor, *m_symbol_prototype);
 
diff --git a/Libraries/LibJS/Runtime/Object.h b/Libraries/LibJS/Runtime/Object.h
index 519c108d73..5da31021d0 100644
--- a/Libraries/LibJS/Runtime/Object.h
+++ b/Libraries/LibJS/Runtime/Object.h
@@ -102,6 +102,7 @@ public:
     virtual bool is_bound_function() const { return false; }
     virtual bool is_native_property() const { return false; }
     virtual bool is_proxy_object() const { return false; }
+    virtual bool is_regexp_object() const { return false; }
     virtual bool is_string_object() const { return false; }
     virtual bool is_symbol_object() const { return false; }
 
diff --git a/Libraries/LibJS/Runtime/RegExpConstructor.cpp b/Libraries/LibJS/Runtime/RegExpConstructor.cpp
new file mode 100644
index 0000000000..9a2198a3f2
--- /dev/null
+++ b/Libraries/LibJS/Runtime/RegExpConstructor.cpp
@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2020, Matthew Olsson <matthewcolsson@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <LibJS/Interpreter.h>
+#include <LibJS/Runtime/Error.h>
+#include <LibJS/Runtime/GlobalObject.h>
+#include <LibJS/Runtime/RegExpConstructor.h>
+#include <LibJS/Runtime/RegExpObject.h>
+
+namespace JS {
+
+RegExpConstructor::RegExpConstructor()
+    : NativeFunction("RegExp", *interpreter().global_object().function_prototype())
+{
+    define_property("prototype", interpreter().global_object().regexp_prototype(), 0);
+    define_property("length", Value(2), Attribute::Configurable);
+}
+
+RegExpConstructor::~RegExpConstructor()
+{
+}
+
+Value RegExpConstructor::call(Interpreter& interpreter)
+{
+    return construct(interpreter);
+}
+
+Value RegExpConstructor::construct(Interpreter& interpreter)
+{
+    if (!interpreter.argument_count())
+        return RegExpObject::create(interpreter.global_object(), "(?:)", "");
+    auto contents = interpreter.argument(0).to_string(interpreter);
+    if (interpreter.exception())
+        return {};
+    auto flags = interpreter.argument_count() > 1 ? interpreter.argument(1).to_string(interpreter) : "";
+    if (interpreter.exception())
+        return {};
+    return RegExpObject::create(interpreter.global_object(), contents, flags);
+}
+
+}
diff --git a/Libraries/LibJS/Runtime/RegExpConstructor.h b/Libraries/LibJS/Runtime/RegExpConstructor.h
new file mode 100644
index 0000000000..76f4321052
--- /dev/null
+++ b/Libraries/LibJS/Runtime/RegExpConstructor.h
@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2020, Matthew Olsson <matthewcolsson@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <LibJS/Runtime/NativeFunction.h>
+
+namespace JS {
+
+class RegExpConstructor final : public NativeFunction {
+public:
+    RegExpConstructor();
+    virtual ~RegExpConstructor() override;
+
+    virtual Value call(Interpreter&) override;
+    virtual Value construct(Interpreter&) override;
+
+private:
+    virtual bool has_constructor() const override { return true; }
+    virtual const char* class_name() const override { return "RegExpConstructor"; }
+};
+
+}
diff --git a/Libraries/LibJS/Runtime/RegExpObject.cpp b/Libraries/LibJS/Runtime/RegExpObject.cpp
new file mode 100644
index 0000000000..d6ce164e98
--- /dev/null
+++ b/Libraries/LibJS/Runtime/RegExpObject.cpp
@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2020, Matthew Olsson <matthewcolsson@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/StringBuilder.h>
+#include <LibJS/Heap/Heap.h>
+#include <LibJS/Interpreter.h>
+#include <LibJS/Runtime/GlobalObject.h>
+#include <LibJS/Runtime/PrimitiveString.h>
+#include <LibJS/Runtime/RegExpObject.h>
+#include <LibJS/Runtime/Value.h>
+
+
+namespace JS {
+
+RegExpObject* RegExpObject::create(GlobalObject& global_object, String content, String flags)
+{
+    return global_object.heap().allocate<RegExpObject>(content, flags, *global_object.regexp_prototype());
+}
+
+RegExpObject::RegExpObject(String content, String flags, Object& prototype)
+    : Object(&prototype)
+    , m_content(content)
+    , m_flags(flags)
+{
+}
+
+RegExpObject::~RegExpObject()
+{
+}
+
+Value RegExpObject::to_string() const
+{
+    return js_string(interpreter(), String::format("/%s/%s", content().characters(), flags().characters()));
+}
+
+}
diff --git a/Libraries/LibJS/Runtime/RegExpObject.h b/Libraries/LibJS/Runtime/RegExpObject.h
new file mode 100644
index 0000000000..5acc72b4ce
--- /dev/null
+++ b/Libraries/LibJS/Runtime/RegExpObject.h
@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2020, Matthew Olsson <matthewcolsson@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <LibJS/AST.h>
+#include <LibJS/Runtime/Object.h>
+
+namespace JS {
+
+class RegExpObject : public Object {
+public:
+    static RegExpObject* create(GlobalObject&, String content, String flags);
+
+    RegExpObject(String content, String flags, Object& prototype);
+    virtual ~RegExpObject() override;
+
+    const String& content() const { return m_content; }
+    const String& flags() const { return m_flags; }
+
+    Value to_string() const override;
+
+private:
+    virtual const char* class_name() const override { return "RegExpObject"; }
+    virtual bool is_regexp_object() const override { return true; }
+
+    String m_content;
+    String m_flags;
+};
+
+}
diff --git a/Libraries/LibJS/Runtime/RegExpPrototype.cpp b/Libraries/LibJS/Runtime/RegExpPrototype.cpp
new file mode 100644
index 0000000000..629d3eadc3
--- /dev/null
+++ b/Libraries/LibJS/Runtime/RegExpPrototype.cpp
@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2020, Matthew Olsson <matthewcolsson@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/Function.h>
+#include <AK/StringBuilder.h>
+#include <LibJS/Heap/Heap.h>
+#include <LibJS/Interpreter.h>
+#include <LibJS/Runtime/GlobalObject.h>
+#include <LibJS/Runtime/PrimitiveString.h>
+#include <LibJS/Runtime/RegExpObject.h>
+#include <LibJS/Runtime/RegExpPrototype.h>
+
+namespace JS {
+
+RegExpPrototype::RegExpPrototype()
+    : RegExpObject({}, {}, *interpreter().global_object().object_prototype())
+{
+}
+
+RegExpPrototype::~RegExpPrototype()
+{
+}
+
+}
diff --git a/Libraries/LibJS/Runtime/RegExpPrototype.h b/Libraries/LibJS/Runtime/RegExpPrototype.h
new file mode 100644
index 0000000000..07c5d51b3a
--- /dev/null
+++ b/Libraries/LibJS/Runtime/RegExpPrototype.h
@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2020, Matthew Olsson <matthewcolsson@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <LibJS/Runtime/RegExpObject.h>
+
+namespace JS {
+
+class RegExpPrototype final : public RegExpObject {
+public:
+    RegExpPrototype();
+    virtual ~RegExpPrototype() override;
+
+private:
+    virtual const char* class_name() const override { return "RegExpPrototype"; }
+};
+
+}
diff --git a/Libraries/LibJS/Token.h b/Libraries/LibJS/Token.h
index 884a249f27..e12747df0b 100644
--- a/Libraries/LibJS/Token.h
+++ b/Libraries/LibJS/Token.h
@@ -113,6 +113,7 @@ namespace JS {
     __ENUMERATE_JS_TOKEN(QuestionMark)                \
     __ENUMERATE_JS_TOKEN(QuestionMarkPeriod)          \
     __ENUMERATE_JS_TOKEN(RegexLiteral)                \
+    __ENUMERATE_JS_TOKEN(RegexFlags)                  \
     __ENUMERATE_JS_TOKEN(Return)                      \
     __ENUMERATE_JS_TOKEN(Semicolon)                   \
     __ENUMERATE_JS_TOKEN(ShiftLeft)                   \
@@ -138,6 +139,7 @@ namespace JS {
     __ENUMERATE_JS_TOKEN(Typeof)                      \
     __ENUMERATE_JS_TOKEN(UnsignedShiftRight)          \
     __ENUMERATE_JS_TOKEN(UnsignedShiftRightEquals)    \
+    __ENUMERATE_JS_TOKEN(UnterminatedRegexLiteral)    \
     __ENUMERATE_JS_TOKEN(UnterminatedStringLiteral)   \
     __ENUMERATE_JS_TOKEN(UnterminatedTemplateLiteral) \
     __ENUMERATE_JS_TOKEN(Var)                         \