I have a simple ES6 class, like so:
class Ring extends Array {
insert (item, index) {
this.splice(index, 0, item);
return this;
}
}
I want to make it so that the indexing for Ring objects wraps, so that new Ring(1, 2, 3)[3]
returns 1, new Ring(1, 2, 3)[-1]
returns 3, and so on. Is this possible in ES6? If so, how would I implement it?
I've read about proxies, which allow a completely customized getter, but I can't figure out how to apply a proxy to a class. I did manage this:
var myRing = new Proxy (Ring.prototype, {
get: function (target, name) {
var len = target.length;
if (/^-?\d+$/.test(name))
return target[(name % len + len) % len];
return target[name];
}
});
myRing
is now a Ring object that supports wrapping indices. The problem is that I'd have to define Ring objects like that every time. Is there a way to apply this proxy to the class such that calling new Ring()
returns it?
Basically it is
class ProxyRing extends Array {
constructor(...args) {
super(...args)
return new Proxy(this, {
get: function (target, name) {
var len = target.length;
if (typeof name === 'string' && /^-?\d+$/.test(name))
return target[(name % len + len) % len];
return target[name];
}
});
}
insert (item, index) {
this.splice(index, 0, item);
return this;
}
}
Warning: This is an ugly hack
This is a rather simple approach when you think about it.
function ClassToProxy(_class, handler) {
return (...args) => new Proxy(new _class(...args), handler);
}
This defined a function ClassToProxy
. The first argument is the class you want to add behavior too, and the second is the handler.
Here's example usage:
const Ring = ClassToProxy(
// Class
class Ring {
constructor(...items) {
this.items = items;
}
},
// Handler
{
get: function(target, name) {
return target.items[name];
}
}
)
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