Enhancement: Add UnionKeys

[Beraliv]

What

I propose type UnionKeys<UnionType>:

• to infer all keys of UnionType
• to support unions

Examples

A type-safe setting value when union is used:

type LogOptions =
  | { action: "openBlogPage"; data: { startTime: number } }
  | { action: "likeVideo"; data: { videoSrc: string } }
  | { action: "closeBlogPage"; data: { readingTime: number } };

const setLogOptions = <TKey extends UnionKeysOf<LogOptions>, TValue = TKey extends keyof LogOptions ? LogOptions[TKey] : never>(
    option: LogOptions,
    key: TKey,
    value: TValue,
) => {
    (option as Record<string, unknown>)[key] = value;
}

declare const option: LogOptions;

setLogOptions(option, 'action', 'openBlogPage');
setLogOptions(option, 'data', {startTime: 1});

Additional Info

TS Playground – https://tsplay.dev/NnE8xw