To Snake Case

1/**
2 * Converts a string to snake_case.
3 *
4 * Handles acronyms and consecutive uppercase letters properly.
5 * Example:
6 *   "XMLHttpRequest" -> "xml_http_request"
7 *
8 * @param str - The input string.
9 * @returns The snake_cased string.
10 *
11 * @example
12 * toSnakeCase("Hello World"); // "hello_world"
13 * toSnakeCase("XMLHttpRequest"); // "xml_http_request"
14 */
15export function toSnakeCase(str: string): string {
16  return (
17    str
18      // Split acronym groups (e.g. "XMLHttp" -> "XML_Http")
19      .replace(/([A-Z]+)([A-Z][a-z])/g, '$1_$2')
20      // Split between a lowercase/digit and an uppercase (e.g. "testHTTP" -> "test_HTTP")
21      .replace(/([a-z\d])([A-Z])/g, '$1_$2')
22      // Replace spaces and dashes with underscores
23      .replace(/[\s-]+/g, '_')
24      .toLowerCase()
25      // Remove leading and trailing underscores
26      .replace(/^_+|_+$/g, '')
27  );
28}