custom regex as type that accepts only matching strings

[antonioconselheiro]

🔍 Search Terms

"regex type", "regular expression type"

✅ Viability Checklist

• [x] This wouldn't be a breaking change in existing TypeScript/JavaScript code
• [x] This wouldn't change the runtime behavior of existing JavaScript code
• [x] This could be implemented without emitting different JS based on the types of the expressions
• [x] This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
• [x] This isn't a request to add a new utility type: https://github.com/microsoft/TypeScript/wiki/No-New-Utility-Types
• [x] This feature would agree with the rest of our Design Goals: https://github.com/Microsoft/TypeScript/wiki/TypeScript-Design-Goals

⭐ Suggestion

Hey people, how are you doing? I would like to suggest use regex as a custom type:

const hexId: /[a-z\d]+/ = 'b9283d50ff2db1d95c08395e73556bc5c147e22125280e78c569603ac6854fe6';

also

type HexString = /[a-z\d]+/;
const hexId: HexString = 'b9283d50ff2db1d95c08395e73556bc5c147e22125280e78c569603ac6854fe6';

I searched through the closed and open issues and didn't find any suggestions exactly like this, but maybe I didn't look hard enough, because it seems like a very obvious suggestion to me.

📃 Motivating Example

This will help me create any custom string type.

💻 Use Cases

1. What do you want to use this for? After validate a string with a regex, by using the regex as type I will be suure that I no need validate that data again.

2. What shortcomings exist with current approaches? I found nothing functional that can bring me something like this.

3. What workarounds are you using in the meantime? I'm using string type and crying.

[Josh-Cena]

https://github.com/microsoft/TypeScript/issues/41160

[antonioconselheiro]

I found this issue, but I was not sure if was exactly that

[MartinJohns]

It is exactly that.

[antonioconselheiro]

closed as duplicated