Is it possible to specify string format with TypeScript?

Question

I just wonder - is it a way to check if the string matches some pattern via TypeScript.

I don't want to do the checks in the runtime.

//What I have now
public id: string; //can be whatever string 

//What I want to see
public id: IdType; //Some type?
id = '0000-0000-0000-0001'//valid
id = 'whatever'//invalid

So is it a way to define string format?

Answer 1

This should now be possible as of TS 4.1 beta

There's now a feature called Template Literal Types, which looks something like this (excuse the basic example):

type idType = `${number}-${number}-${number}-${number}`
const id: idType = '0000-0000-0000-0001';

https://devblogs.microsoft.com/typescript/announcing-typescript-4-1-beta/#template-literal-types

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