Typescript split string and validate type

Question

Let's say i have a string value of ReplaceText::some.other.property, I'd like to split this value by the delimeter of :: and validate the types of each input

type Action = 'ReplaceText' | 'ReplaceImage';

type Split<S extends string, D extends string> =
    string extends S ? Action[] :
    S extends '' ? [] :
    S extends `${infer T}${D}${infer U}` ? [T, ...Split<U, D>] : [S];
    

declare function translate<P extends string>(path: P): Split<P, '::'>;
const [action, dotString] = translate('ReplaceText::some.other.property');

This returns the values, but action is not of type of Action, I'm not quite sure where to begin here!

eg, if i did:

const [action, dotString] = translate('ActionThatDoesNotExist::some.other.property');
// id expect validation errors because this action does not exist!

Sorry, I've fixed up my typos!

Shannon Hochkins
– Shannon Hochkins

2022-12-19 22:52:05 +00:00
Commented Dec 19, 2022 at 22:52 — Shannon Hochkins
– Shannon Hochkins, Commented Dec 19, 2022 at 22:52

Alex Wayne · Accepted Answer · 2022-12-19 23:09:15Z

2

You just need to use a string literal type like:

type Action = 'ReplaceText' | 'ReplaceImage';
type ActionWithPath = `${Action}::${string}`

Now ActionWithPath is any string that starts with an Action, followed by :: and then any string.

Then just use that type as your constraint:

declare function translate<P extends ActionWithPath>(path: P): Split<P, '::'>;

And the rest works like you expect:

translate('ReplaceText::some.other.property'); // fine
translate('ActionThatDoesNotExist::some.other.property'); // error

See playground

Note: deriving a dotted object path is much trickier and out of scope of this question, but you can start here: Typescript: deep keyof of a nested object

answered Dec 19, 2022 at 23:09

Alex Wayne

188k52 gold badges328 silver badges363 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Shannon Hochkins Over a year ago

I actually have already solved the dot notated part :)

Collectives™ on Stack Overflow

Typescript split string and validate type

1 Answer 1

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related