how to process constants in typescript?

Question

I have a react component like so:

const myComponent = ({constant}: Iprops) => (
  <div>
    {CONSTANTS[constant].property ? <showThis /> : null
  </div>
)

it's complaining that element implicitly has an 'any' type because type 'object' has no index signature

how do I add CONSTANTS to my interface? I've tried

interface IProps {
    [CONSTANTS: any]: {
        constant: boolean;
    }
}

but obviously it doesn't like that. how can I declare the type of each key in my object?

thanks

What does CONSTANTS look like? Please, post the entire class. — , Jan 28 '19 at 10:20

score 1 · Answer 1 · answered Jan 28 '19 at 17:52

I'm not sure I understanf the shape of the objects you actually need. But you can type an object with this syntax:

const CONSTANTS: { [key:string]: boolean } = {}
CONSTANTS["something1"] = false; // ok
CONSTANTS["something2"] = "Hey"; // not ok

It's a bit tricky as the key can actually be either string or number but the value type is properly enforced so you can still have more complex types there instead of a boolean.

how to process constants in typescript?

1 Answers1