Showing posts from December, 2020

TypeScript: Turn an Array of Values into a Type Union

I found the answer I was looking for here: I wasn't sure that it would be possible. In fact, it turns out that the solution is far more impressive than I expected. What follows cuts to the core part of the article that I need solved my particular problem. Problem I want to have an object type with specific keys and I want a static array of those keys, but I don't want to have the same list of keys written out twice in case I mistakenly make them differ in the future. type K = "a" | "b" | "c"; type O = Record<K, V>; const keys: K[] = ["a","b","c"]; I want to be sure that 'keys' contains every member of type 'K' exactly once and vice-versa. I want to use 'keys' to build an object of type 'O', so I can't just rely on using 'Object.keys' on an existing object. Solution const keys = ["