Caveat: I am aware that what I’m suggesting might clash too hardly with current
semantics (how to handle invocation, apply(), call(), etc.), but I am
interested in the arguments against it.
>> (1) I would prefer non-method functions not to have a binding for |this| at
>> all.
>
> How do you define "non-method"?
A function that is not invoked as method. Right now, the same kind of construct
is used for both true functions and methods. I’m proposing a new construct
(similar to the distinction that Python makes): a function that does not have
an implicit |this| parameter.
> It would make an early error for many functions written today as function
> declarations, which use |this| because they are assigned as property values
> (i.e. as methods), to call the |this| usage in such functions an early error.
> That would be a harsh migration tax, even though compile-time. We are not
> changing Harmony that much.
Right. It could be introduced via the arrow function syntax, with the
"function" operator remaining as is:
var obj = {
id: "123",
method: (x) => { // same as function operator
[1,2].forEach((i) -> { // new construct
console.log(this.id + ": " + i + " - " + x);
});
}
}
Thus:
=> and function: |this| is an implicit argument (“methods”)
->: |this| is not an implicit argument; currently simulated via binding
(“functions”)
The arrows are swapped compared to the strawman, because => is more
“heavy-weight” here.
>> Isn’t (1) a better solution?
>
> Why?
It is easier to understand for beginners. |this| always being an implicit
parameter trips up many newbies. I also find it a cleaner way of getting
lexical |this|.
>> I’m assuming (2) is done, because (1) would be too radical a change
>> (execution contexts etc.)?
>
> Think migration tax. Many functions whether declared or expressed use |this|
> today. They are used as methods but the linkage to their method name
> (property of an object) is not declared or even expressed nearby. How would
> you forbid such functions to use |this|, or allow them to but forbid others
> that are not called as methods to use |this|/
See above.
Greetings,
Axel
--
Dr. Axel Rauschmayer
[email protected]
twitter.com/rauschma
home: rauschma.de
blog: 2ality.com
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