New String methods for TS 4.1+

[mikeplus64]

Now that string templating is possible it's possible to build your own type-level parsers and formatters. Here's what I'd suggest as a start:

type Intersperse<L extends List<string|number|bigint>, Sep extends string|number|bigint> = ...

type Split<L extends List<string|number|bigint>, Sep extends string|number|bigint> = ...

type Concat<L extends List<string|number|bigint> = ...

type StartsWith<S extends string, Prefix extends string> = ...

type EndsWith<S extends string, Suffix extends string> = ...

Motivation

Writing a type-safe routing library, these are utility types that I've mostly already defined.

[millsp]

Hey @mikeplus64, thanks! We should definitely add this. Would you like to open a PR?

[mikeplus64]

Yep can do next week some time.

[ghost]

Hi guys,

would you consider support of object keys case transformation to *Case types (like SnakeCase, CamelCase, DashCase etc.)?

Another library called type-fest already supports these types. Also, here is trivial implementation of SnakeCase to CamelCase scenario, although I am not qualified to check correctness of the implementation, which seems to be surprisingly simple.

There are many use cases for this kind of feature, for example when handling difference of object keys case between front-end and back-end apps, where you usually struggling with camel-case to snake-case transformations and vice versa in request/response payloads.

By the way, I was wondering if there is library which transforms object keys case at runtime and I found this one - change-case. Although I didn't use it yet, it may offers a simple solution to described problem in combinations with proposed *Case types.