transformCamelSnakeCase

1/**
2 * Converts between camelCase and snake_case formats.
3 *
4 * @param str - The input string.
5 * @param direction - Direction of transformation: 'camelToSnake' or 'snakeToCamel'.
6 * @returns Transformed string in the desired format.
7 */
8export function transformCamelSnakeCase(
9  str: string,
10  direction: 'camelToSnake' | 'snakeToCamel'
11): string {
12  if (direction === 'camelToSnake') {
13    return str.replace(/([a-z])([A-Z])/g, '$1_$2').toLowerCase();
14  }
15
16  if (direction === 'snakeToCamel') {
17    return str.replace(/_([a-z])/g, (_, char) => char.toUpperCase());
18  }
19
20  throw new Error('Invalid direction: use "camelToSnake" or "snakeToCamel"');
21}

1test('transformCamelSnakeCase - camel to snake', () => {
2  expect(transformCamelSnakeCase('myVariableName', 'camelToSnake')).toBe('my_variable_name');
3});
4
5test('transformCamelSnakeCase - snake to camel', () => {
6  expect(transformCamelSnakeCase('my_variable_name', 'snakeToCamel')).toBe('myVariableName');
7});
8
9test('transformCamelSnakeCase - empty string', () => {
10  expect(transformCamelSnakeCase('', 'camelToSnake')).toBe('');
11  expect(transformCamelSnakeCase('', 'snakeToCamel')).toBe('');
12});
13
14test('transformCamelSnakeCase - no uppercase in camel', () => {
15  expect(transformCamelSnakeCase('simple', 'camelToSnake')).toBe('simple');
16});
17
18test('transformCamelSnakeCase - invalid direction throws', () => {
19  expect(() => transformCamelSnakeCase('test', 'wrong' as any)).toThrow(
20    'Invalid direction: use "camelToSnake" or "snakeToCamel"'
21  );
22});