ts-case-transformer/dist/types.d.ts

A TypeScript utility for transforming object keys between different case styles with full type safety

export type CaseType = 'camelCase' | 'snake_case' | 'kebab-case' | 'PascalCase' | 'flatcase' | 'UPPERFLATCASE' | 'Pascal_Snake_Case' | 'camel_Snake_Case' | 'SCREAMING_SNAKE_CASE';
type WordSeparators = '-' | '_' | ' ' | '.';
type UpperChar<C extends string> = Uppercase<C> extends C ? true : false;
type SplitWords<S extends string, Acc extends string = ''> = S extends `${infer First}${infer Rest}` ? First extends WordSeparators ? [Acc, ...SplitWords<Rest>] : UpperChar<First> extends true ? Acc extends '' ? SplitWords<Rest, First> : [Acc, ...SplitWords<`${First}${Rest}`>] : SplitWords<Rest, `${Acc}${First}`> : Acc extends '' ? [] : [Acc];
type ToCamelWords<Words extends string[]> = Words extends [
    infer First extends string,
    ...infer Rest extends string[]
] ? `${Lowercase<First>}${Rest extends [] ? '' : `${Capitalize<ToCamelWords<Rest>>}`}` : '';
type ToSnakeWords<Words extends string[]> = Words extends [
    infer First extends string,
    ...infer Rest extends string[]
] ? `${Lowercase<First>}${Rest extends [] ? '' : `_${ToSnakeWords<Rest>}`}` : '';
type ToKebabWords<Words extends string[]> = Words extends [
    infer First extends string,
    ...infer Rest extends string[]
] ? `${Lowercase<First>}${Rest extends [] ? '' : `-${ToKebabWords<Rest>}`}` : '';
type ToPascalWords<Words extends string[]> = Words extends [
    infer First extends string,
    ...infer Rest extends string[]
] ? `${Capitalize<Lowercase<First>>}${ToPascalWords<Rest>}` : '';
type ToFlatWords<Words extends string[]> = Words extends [
    infer First extends string,
    ...infer Rest extends string[]
] ? `${Lowercase<First>}${ToFlatWords<Rest>}` : '';
type ToUpperFlatWords<Words extends string[]> = Words extends [
    infer First extends string,
    ...infer Rest extends string[]
] ? `${Uppercase<First>}${ToUpperFlatWords<Rest>}` : '';
type ToPascalSnakeWords<Words extends string[]> = Words extends [
    infer First extends string,
    ...infer Rest extends string[]
] ? `${Capitalize<Lowercase<First>>}${Rest extends [] ? '' : `_${ToPascalSnakeWords<Rest>}`}` : '';
type ToCamelSnakeWords<Words extends string[]> = Words extends [
    infer First extends string,
    ...infer Rest extends string[]
] ? `${Lowercase<First>}${Rest extends [] ? '' : `_${ToPascalSnakeWords<Rest>}`}` : '';
type ToScreamingSnakeWords<Words extends string[]> = Words extends [
    infer First extends string,
    ...infer Rest extends string[]
] ? `${Uppercase<First>}${Rest extends [] ? '' : `_${ToScreamingSnakeWords<Rest>}`}` : '';
export type ToCamelCase<S extends string> = ToCamelWords<SplitWords<S>>;
export type ToSnakeCase<S extends string> = ToSnakeWords<SplitWords<S>>;
export type ToKebabCase<S extends string> = ToKebabWords<SplitWords<S>>;
export type ToPascalCase<S extends string> = ToPascalWords<SplitWords<S>>;
export type ToFlatCase<S extends string> = ToFlatWords<SplitWords<S>>;
export type ToUpperFlatCase<S extends string> = ToUpperFlatWords<SplitWords<S>>;
export type ToPascalSnakeCase<S extends string> = ToPascalSnakeWords<SplitWords<S>>;
export type ToCamelSnakeCase<S extends string> = ToCamelSnakeWords<SplitWords<S>>;
export type ToScreamingSnakeCase<S extends string> = ToScreamingSnakeWords<SplitWords<S>>;
type CaseMapping<S extends string, C extends CaseType> = C extends 'camelCase' ? ToCamelCase<S> : C extends 'snake_case' ? ToSnakeCase<S> : C extends 'kebab-case' ? ToKebabCase<S> : C extends 'PascalCase' ? ToPascalCase<S> : C extends 'flatcase' ? ToFlatCase<S> : C extends 'UPPERFLATCASE' ? ToUpperFlatCase<S> : C extends 'Pascal_Snake_Case' ? ToPascalSnakeCase<S> : C extends 'camel_Snake_Case' ? ToCamelSnakeCase<S> : C extends 'SCREAMING_SNAKE_CASE' ? ToScreamingSnakeCase<S> : never;
export type Transformers = {
    [K in CaseType]: (str: string) => string;
};
export type TransformObjectKeys<T, Case extends CaseType> = T extends Array<infer U> ? Array<U extends object ? TransformObjectKeys<U, Case> : U> : T extends object ? {
    [K in keyof T as CaseMapping<K & string, Case>]: T[K] extends object ? TransformObjectKeys<T[K], Case> : T[K];
} : T;
export {};