camelToSnakeCase.js

function convertCamelCaseToSnakeCase(text) {
  const inputLines = text.split('\n');
  const outputLines = inputLines.map((line) => {
    return Array.from(line).reduce((acc, v, i) => {
      if (i == 0) {
        acc += v.toLocaleLowerCase();
        return acc;
      }
      if (v.toLocaleUpperCase() == v) {
        acc += '_';
      }
      acc += v.toLocaleLowerCase();
      return acc;
    }, '');
  });
  return outputLines.join('\n');
}