Other than the JQuery style misuse of this, what are the
use cases? If you want to bind this, why wouldn't a method
invocation on an objet be involved?
The ES array loops accept an optional this parameter to
be used for the loop callback.
It is up to the caller of the forEach to provide both the callback
function and the optional this arg. So the caller has the option
on both the kind of function passed and whether a this value is
needed.
..
in other-words, it is available as an alternative to saying:
logAll: function() {
var self = this;
this.state.forEach(function(v) {self.log(v)});
}
..
Arrow functions need to eliminate the need for such idioms
that get around unwanted dynamic this bindings.
Another way to look at these higher-order methods is that they
split plain methods into framework (eg loop) and callbacks (eg
loop body). Only the framework is directly attached to the object
(eg Array), while the callbacks are passed in from the outside.
Passing the framework this to the callback brings framework
and callback together again. One can write the callback as if it
was part of the object method.
No, there's nothing wrong with your wrappering, but I'm not
sure why it would be needed. You code code the above as:
logAll: function() {this.state.forEach(fn((it,v)-> it.log(v)),this)};
but why would you? Particularly since you have to name the
explicit initial this-like argument in the arrow something other
than "this".
I'm not saying that this is needed, only that we can account for
this use case without changing arrow functions. And I was
surprised that both pro and cons camps continued the discussion
of recursive self and dynamic this naming as if no workaround
was available.
To me, the ability to emulate the feature additions so closely in
library functions suggests that some variation of fn and rec
should go into the standard library instead of adding such
features to arrow functions. But perhaps there are reasons for
preferring the language features over the library functions?
Claus
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