type-fest
Version:
A collection of essential TypeScript types
48 lines (39 loc) • 1.12 kB
TypeScript
import type {IsNumericLiteral} from './is-literal';
import type {IsNegative} from './numeric';
/**
Returns a new string which contains the specified number of copies of a given string, just like `String#repeat()`.
@example
```
import {StringRepeat} from 'type-fest';
declare function stringRepeat<
Input extends string,
Count extends number
>(input: Input, count: Count): StringRepeat<Input, Count>;
// The return type is the exact string literal, not just `string`.
stringRepeat('foo', 2);
//=> 'foofoo'
stringRepeat('=', 3);
//=> '==='
```
@category String
@category Template literal
*/
export type StringRepeat<
Input extends string,
Count extends number,
> = StringRepeatHelper<Input, Count>;
type StringRepeatHelper<
Input extends string,
Count extends number,
Counter extends never[] = [],
Accumulator extends string = '',
> =
IsNegative<Count> extends true
? never
: Input extends ''
? ''
: Count extends Counter['length']
? Accumulator
: IsNumericLiteral<Count> extends false
? string
: StringRepeatHelper<Input, Count, [...Counter, never], `${Accumulator}${Input}`>;