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LibJS: Allow the choice of a scope of declaration for a variable (#1408)

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Previously, we were assuming all declared variables were bound to a
block scope, now, with the addition of declaration types, we can bind
a variable to a block scope using `let`, or a function scope (the scope
of the inner-most enclosing function of a `var` declaration) using
`var`.
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0xtechnobabble 2020-03-11 21:09:20 +02:00 • committed by GitHub
parent 542108421e
commit df40c85f80
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6 changed files with 85 additions and 16 deletions
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33
Userland/js.cpp
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@ -92,10 +92,12 @@ void build_program(JS::Program& program)
auto block = make<JS::BlockStatement>();
block->append<JS::VariableDeclaration>(
make<JS::Identifier>("a"),
make<JS::Literal>(JS::Value(5)));
make<JS::Literal>(JS::Value(5)),
JS::DeclarationType::Var);
block->append<JS::VariableDeclaration>(
make<JS::Identifier>("b"),
make<JS::Literal>(JS::Value(7)));
make<JS::Literal>(JS::Value(7)),
JS::DeclarationType::Var);
block->append<JS::ReturnStatement>(
make<JS::BinaryExpression>(
@ -120,13 +122,38 @@ void build_program(JS::Program& program)
auto block = make<JS::BlockStatement>();
block->append<JS::VariableDeclaration>(
make<JS::Identifier>("x"),
make<JS::ObjectExpression>());
make<JS::ObjectExpression>(),
JS::DeclarationType::Var);
block->append<JS::CallExpression>("$gc");
program.append<JS::FunctionDeclaration>("foo", move(block));
program.append<JS::CallExpression>("foo");
}
#elif PROGRAM == 4
void build_program(JS::Program& program)
{
// function foo() {
// function bar() {
// var y = 6;
// }
//
// bar()
// return y;
// }
// foo(); //I should return `undefined` because y is bound to the inner-most enclosing function, i.e the nested one (bar()), therefore, it's undefined in the scope of foo()
auto block_bar = make<JS::BlockStatement>();
block_bar->append<JS::VariableDeclaration>(make<JS::Identifier>("y"), make<JS::Literal>(JS::Value(6)), JS::DeclarationType::Var);
auto block_foo = make<JS::BlockStatement>();
block_foo->append<JS::FunctionDeclaration>("bar", move(block_bar));
block_foo->append<JS::CallExpression>("bar");
block_foo->append<JS::ReturnStatement>(make<JS::Identifier>("y"));
program.append<JS::FunctionDeclaration>("foo", move(block_foo));
program.append<JS::CallExpression>("foo");
}
#elif PROGRAM == 5
void build_program(JS::Program& program, JS::Heap& heap)
{
// "hello friends".length