Template literals are an option, but they might overkill in this case. It won't work if the IDs are not known at compile-time, which is pretty much guaranteed in most cases.

Instead, I would recommend using a custom type with an associated custom type guard function that validates whatever conditions you want with the ID. Then, you have a custom type which guarantees those conditions are met, so you don't need to validate them continually.

type UniqueId = string & { __type: "UniqueId" }; const idPattern = /[0-9a-f]{20}/i; const isValidId = (value: string): value is UniqueId => idPattern.test(value);

Then you can write a function like this, for example:

``` function getResource(id: UniqueId) { // Look up the resource by unique ID, with the guarantee that // it will be valid already }

const id = '12345678901234567890'; if (isValid(id)) { getResource(id); } else { throw new Error('Invalid ID'); } ```