type-fest/source/string-slice.d.ts

A collection of essential TypeScript types

import type {Join} from './join';
import type {ArraySlice} from './array-slice';
import type {StringToArray} from './internal';

/**
Returns a string slice of a given range, just like `String#slice()`.

@see {ArraySlice}

@example
```
import type {StringSlice} from 'type-fest';

StringSlice<'abcde', 0, 2>;
//=> 'ab'

StringSlice<'abcde', 1>;
//=> 'bcde'

StringSlice<'abcde', 0, -1>;
//=> 'abcd'

StringSlice<'abcde', -2, -1>;
//=> 'd'
```

@category String
*/
export type StringSlice<
	S extends string,
	Start extends number = 0,
	End extends number = StringToArray<S>['length'],
> = string extends S
	? string[]
	: ArraySlice<StringToArray<S>, Start, End> extends infer R extends readonly string[]
		? Join<R, ''>
		: never;