LibJS: Allow reserved words as keys in object expressions.

Author: https://github.com/sunverwerth
Commit: bf5b251684
Pull-request: https://github.com/SerenityOS/serenity/pull/1849
Issue: https://github.com/SerenityOS/serenity/issues/1768

Libraries/LibJS/Token.cpp

@@ -129,4 +129,44 @@ bool Token::bool_value() const
     return m_value == "true";
 }
 
+bool Token::is_identifier_name() const
+{
+    // IdentifierNames are Identifiers + ReservedWords
+    // The standard defines this reversed: Identifiers are IdentifierNames except reserved words
+    // https://www.ecma-international.org/ecma-262/5.1/#sec-7.6
+    return m_type == TokenType::Identifier
+        || m_type == TokenType::Await
+        || m_type == TokenType::BoolLiteral
+        || m_type == TokenType::Break
+        || m_type == TokenType::Case
+        || m_type == TokenType::Catch
+        || m_type == TokenType::Class
+        || m_type == TokenType::Const
+        || m_type == TokenType::Continue
+        || m_type == TokenType::Default
+        || m_type == TokenType::Delete
+        || m_type == TokenType::Do
+        || m_type == TokenType::Else
+        || m_type == TokenType::Finally
+        || m_type == TokenType::For
+        || m_type == TokenType::Function
+        || m_type == TokenType::If
+        || m_type == TokenType::In
+        || m_type == TokenType::Instanceof
+        || m_type == TokenType::Interface
+        || m_type == TokenType::Let
+        || m_type == TokenType::New
+        || m_type == TokenType::NullLiteral
+        || m_type == TokenType::Return
+        || m_type == TokenType::Switch
+        || m_type == TokenType::This
+        || m_type == TokenType::Throw
+        || m_type == TokenType::Try
+        || m_type == TokenType::Typeof
+        || m_type == TokenType::Var
+        || m_type == TokenType::Void
+        || m_type == TokenType::While
+        || m_type == TokenType::Yield;
+}
+
 }