Set property of a class using a variable

Question

Is something like this possible?

const propName = "x";

class A {
    static propName = 1
    // equivalent to static x = 1
}

A[propName] // evaluates to 1

or would it be (typeof A)[propName]?

For obvious reasons, this is not a duplicate of this question

@PatrickRoberts Did you read this question? It's completely different to what you marked as a duplicate... — Tobiq
– Tobiq, Commented Mar 4, 2019 at 2:24
I read the question. There is no property named x, just a property named propName. So either A.propName or const propName = "propName"; — Patrick Roberts
– Patrick Roberts, Commented Mar 4, 2019 at 2:25
@PatrickRoberts You should re-open this question. I have no idea why you think that other question is even related - it's not even TypeScript — Tobiq
– Tobiq, Commented Mar 4, 2019 at 2:27
That is not equivalent to static x = 1, FYI. The meaning of static propName = 1 does not change just because a string variable propName exists. — Patrick Roberts
– Patrick Roberts, Commented Mar 4, 2019 at 2:31

Tobiq · Accepted Answer · 2019-03-04 02:33:08Z

2

This is possible, simply as:

const propName = "x";

class A {
    static [propName] = 1
    // equivalent to static x = 1
}

A[propName]

answered Mar 4, 2019 at 2:33

Tobiq

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4 Comments

Patrick Roberts Over a year ago

1) Don't assume it's me downvoting. 2) A[propName] will compile regardless of whether x exists on A or not. Try it yourself. This is not type-safe, see this.

Patrick Roberts Over a year ago

Yes

jcalz Over a year ago

This answer is correct; it is using computed properties, which TypeScript understands as long as the value of the property is statically known as a literal type (so let propName = "x"; would fail because propName would be string).

jcalz Over a year ago

And as for A[propName] compiling whether or not x exists on A: you would get a warning with --strict or --noImplicitAny modes.

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