Creates a new type that allows you to convert object's properties' case from `snake_case` to `camelCase`. This could be useful for reducing code duplication when you need respective model for TS code (camelCase) and REST request/response (JSON; snake_case).

SnakeToCamelCase.ts

type DB = {aaa_bbb: string, ccc_ddd_eee_fff: number};
type TS = {ab: string, cd: number};
declare function toTS(db: DB): TS;  // etc....

type ArrayElementType<T> = T extends (infer E)[] ? E : never;

const el1: ArrayElementType<string[]> = 'hello';
const el2: ArrayElementType<string[]> = 1;

type helloLiteral = 'hello';
const hello: `${helloLiteral}` = 'hello';

type FistPart<T extends string> = T extends `${infer S}!${infer _}` ? S : never;
const testx: FistPart<'any'> = 'hello';
const testy: FistPart<'any!type'> = 'any';


type SnakeToPascalCase<T extends string> = T extends `${infer S1}_${infer S2}` ?
    `${Capitalize<S1>}${Capitalize<S2>}` :
    T extends `${infer S}` ? Capitalize<S> : never;

type SnakeToCamelCase<T extends string> = T extends `${infer S1}_${infer S2}_${infer S3}` ?
    `${SnakeToCamelCase<S1>}${SnakeToPascalCase<S2>}${SnakeToPascalCase<S3>}` :
    T extends `${infer R1}_${infer R2}` ? `${R1}${Capitalize<R2>}`
        : T extends `${infer S}` ? S : never;


type DBwithCamelCaseProps = {
  [Key in keyof DB as SnakeToCamelCase<Key>]: DB[Key]
}

const testCamelCaseDB: DBwithCamelCaseProps = {
  aaaBbb: 'hello',
  cccDddEeeFff: 42,
}