One probably should separate
two concerns: providing a default value vs. adding missing values to the
collection.
One possible signature:
function get(key, default = undefined, addIfMissing = false)
The
above would also allow you to store `undefined` and detect missing
values, by using a special value (e.g. named NO_VALUE) as the default.
Hi,
I recently
wrote some code using WeakMaps and the following pattern
keeps coming
over and over:
-----
var v = wm.get(o);
if(v === undefined){
v = someValue;
order.set(o, v);
}
// now, wn has a
value for o (either it already did or it's been added)
// v ===
wm.get(o)
// play with v
-----
The "v === undefined" is
fine in my case, because I know I never store
"undefined" as a value.
I
thought that maybe the semantics of WeakMap#get could be changed
whenever
the key is not used to set the value and return it.
My pattern would
be reduced to:
-----
var v = wm.get(o, someValue);
// now, wn
has a value for o (either it already did or it's been added)
// v ===
wm.get(o)
// play with v
-----
Thinking more about the
current semantics, I thought that what is
currently done could be
achieved a bit differently:
-----
var v = wm.get(o, def);
//
almost equivalent to:
var v = wm.get(o) || def;
-----
There is a
difference when the vaue stored in the weak map is a falsy value.
My
personal experience is to store mostly objects (so truthy) as weak
map
values, so I wouldn't be affected. Has anyone else experience in
storing
falsy values?
David
_______________________________________________
es-discuss
mailing list
[email protected]https://mail.mozilla.org/listinfo/es-discuss
