Since declarations are now hoisted and handled on scope entry, the job
of a VariableDeclaration becomes to actually initialize variables.
As such, we can remove the part where we insert variables into the
nearest relevant scope. Less work == more speed! :^)
"var" declarations are hoisted to the nearest function scope, while
"let" and "const" are hoisted to the nearest block scope.
This is done by the parser, which keeps two scope stacks, one stack
for the current var scope and one for the current let/const scope.
When the interpreter enters a scope, we walk all of the declarations
and insert them into the variable environment.
We don't support the temporal dead zone for let/const yet.
The MDN example for creating a custom error type in javascript uses:
function CustomError(foo, message, fileName, lineNumber) {
var instance = new Error(message, fileName, lineNumber);
instance.name = 'CustomError';
instance.foo = foo;
Object.setPrototypeOf(instance, Object.getPrototypeOf(this));
return instance;
}
The name property on the Error prototype needs to be settable for
this to work properly.
The output of FunctionPrototype::to_string is now more in line
with the output in Firefox. The builtin constructors have been
extended to include their function name in the output.
We were hitting strcmp() in every variable lookup to see if the lookup
was for "this". Caching a FlyString("this") turns that check into one
pointer comparison instead. :^)
This patch adds instance, constructor and prototype classes for:
- EvalError
- InternalError
- RangeError
- ReferenceError
- SyntaxError
- TypeError
- URIError
Enumerator macros are used to reduce the amount of typing. :^)
Object.defineProperty() can now change the attributes of a property
already on the object. Internally this becomes a shape transition with
the TransitionType::Configure. Such transitions don't expand the
property storage capacity, but rather simply keep attributes up to date
when generating a property table.
We now care (a little bit) about the "configurable" and "writable"
property attributes.
Property attributes are stored together with the property name in
the Shape object. Forward transitions are not attribute-savvy and will
cause poor Shape reuse in the case of multiple same-name properties
with different attributes.
Oh, and this patch also adds Object.getOwnPropertyDescriptor() :^)
We already have "global" as a way to access the global object in js(1)
(both REPL and script mode). This replaces it with "globalThis", which
is available in all environments, not just js.
This patch adds very basic XMLHttpRequest support to LibWeb. Here's an
example that currently works:
var callback = function() { alert(this.responseText); }
var xhr = new XMLHttpRequest();
xhr.addEventListener("load", callback);
xhr.open("GET", "http://serenityos.org/~kling/test/example.txt");
xhr.send();
There are many limitations and bugs, but it's pretty dang awesome that
we have XHR. :^)
Many other parsers call it with this name.
Also Type can be confusing in this context since the DeclarationType is
not the type (number, string, etc.) of the variables that are being
declared by the VariableDeclaration.
