I have array of objects
const data = [{ test: 'first'}, { test: 'second'} ]
How I can get union type that looks like:
const TestType = 'first' | 'second'
from this array?
Probably we can infer it somehow, or?
>Solution :
So there is actually a way to do this.
For it to work though you would need to include an as const assertion to the data array.
Example:
const data = [{ test: 'first'}, { test: 'second'} ] as const
const dataForType = [...data.map(d => d.test)]
type TestType = typeof dataForType[number];
So basically we create a new array, iterate over the original data array and return the values of all corresponding test keys.
Then we create a union type that is the culmination of all these values.
Perhaps there is a shorter way to write this, but this is the gist of it.