This code works:
class Test {
#field
get field() {
return this.#field;
}
}
But if I want to calculate field name I have to use square brackets but it doesn't work:
class Test {
#field;
get field() {
return this['#field'];
}
}
Is there any way to get private field with calculated name?
This is not possible. From the proposal:
There are no private computed property names:
#foois a private identifier, and#[foo]is a syntax error.
and its FAQ:
Why doesn't
this['#x']access the private field named#x, given thatthis.#xdoes?
This would complicate property access semantics.
Dynamic access to private fields is contrary to the notion of 'private'. E.g. this is concerning:
class Dict extends null { #data = something_secret; add(key, value) { this[key] = value; } get(key) { return this[key]; } } (new Dict).get('#data'); // returns something_secretBut doesn't giving
this.#xandthis['#x']different semantics break an invariant of current syntax?Not exactly, but it is a concern.
this.#xhas never previously been legal syntax, so from one point of view there can be no invariant regarding it.On the other hand, it might be surprising that they differ, and this is a downside of the current proposal.
See also this issue.
It looks like it is a problem to hand over a string which has a special meaning.
If really necessary, you evaluate a string.
class Test {
#field = 'foo';
get field() {
return eval('this.' +'#field');
}
}
console.log(new Test().field)
#for private class member is still experimental and shouldn't be used for production systems. (Firefox doesn't support it) Also, it's not intended to be used in[]. If you want to have dynamic fields, you could dothis.#fields['myfield'];where#fieldswas declared like#fields = {field1: 1, field2: "a"};.#foois a private identifier, and#[foo]is a syntax error."