Trim but with characters other than whitespace

[danielo515]

Hello!

Today I found myself in a situation where I had to remove the numbers at the end of each string of one union type.
This is because I have my color tokens defined as an union of grey1 | grey2 | greyNN | red1 | red2 | redNN and I wanted just the name part for a function that was going to compose them, something like this:

function doSomething (color: string) {
return { bg: `${color}1`, text: `${color}11` } 
}

And I wanted to make sure that I only passed valid colors. But for that I need the list without the number at the end.
I was surprised of how easy was to encode this using type-fest:

import { Split } from 'type-fest';
type Digit = '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9';
type NumberAtEnd = `${string}${Digit}`;

export type RemoveNumbers<S extends string> = S extends `${NumberAtEnd}${Digit}`
  ? RemoveNumbers<Split<S, Digit>[0]>
  : Split<S, Digit>[0];

What do you think about adding this utility to the library? It can easily be extended to do a maximum of N digits. To be honest, I don't think anyone will need anything more than 2 or 3 or else you are doing something probably wrong

Regards

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[sindresorhus]

This feels a bit niche. Can you think of any other use-cases for this? Or maybe a way to make the utility a bit more general?

[danielo515]

The only use case I think now is the one I had with color tokens (which I would say is a big one for FE people).
Maybe providing the type to remove from the tail could make it more general? Like if you want to remove a suffix, or a list of suffixes? But I don't know how more hard that may be.

[sindresorhus]

I think a RemovePrefix and RemoveSuffix type would be more generally useful.

[fregante]

This is just TrimLeft/TrimRight but with '1234567890' as characters

This implementation might work: #134 (comment)