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LibJS: Add basic support for (scoped) variables

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It's now possible to assign expressions to variables. The variables are
put into the current scope of the interpreter.

Variable lookup follows the scope chain, ending in the global object.
This commit is contained in:
Andreas Kling 2020-03-09 21:13:55 +01:00
parent ac3c19b91c
commit 1382dbc5e1
5 changed files with 224 additions and 19 deletions
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60
Libraries/LibJS/AST.cpp
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@ -393,4 +393,64 @@ void WhileStatement::dump(int indent) const
body().dump(indent + 1);
}
Value Identifier::execute(Interpreter& interpreter) const
{
return interpreter.get_variable(string());
}
void Identifier::dump(int indent) const
{
print_indent(indent);
printf("Identifier \"%s\"\n", m_string.characters());
}
Value AssignmentExpression::execute(Interpreter& interpreter) const
{
ASSERT(m_lhs->is_identifier());
auto name = static_cast<const Identifier&>(*m_lhs).string();
auto rhs_result = m_rhs->execute(interpreter);
switch (m_op) {
case AssignmentOp::Assign:
interpreter.set_variable(name, rhs_result);
break;
}
return rhs_result;
}
void AssignmentExpression::dump(int indent) const
{
const char* op_string = nullptr;
switch (m_op) {
case AssignmentOp::Assign:
op_string = "=";
break;
}
ASTNode::dump(indent);
print_indent(indent + 1);
printf("%s\n", op_string);
m_lhs->dump(indent + 1);
m_rhs->dump(indent + 1);
}
Value VariableDeclaration::execute(Interpreter& interpreter) const
{
interpreter.declare_variable(name().string());
if (m_initializer) {
auto initalizer_result = m_initializer->execute(interpreter);
interpreter.set_variable(name().string(), initalizer_result);
}
return js_undefined();
}
void VariableDeclaration::dump(int indent) const
{
ASTNode::dump(indent);
m_name->dump(indent + 1);
if (m_initializer)
m_initializer->dump(indent + 1);
}
}