keysToCamel.js

const isArray = function (a) {
  return Array.isArray(a);
};

const isObject = function (o) {
  return o === Object(o) && !isArray(o) && typeof o !== 'function';
};

const toCamel = s => (
  s.replace(/([-_][a-z])/ig, $1 => $1.toUpperCase().replace(/[-_]/, ''))
);

const keysToCamel = (o) => {
  if (isObject(o)) {
    return Object.fromEntries(
      Object.entries(o).map(([k, v]) => [toCamel(k), keysToCamel(v)]),
    );
  }

  if (isArray(o)) {
    return o.map(keysToCamel);
  }

  return o;
};

const o = {
  foo_bar: 42,
  something_else: [
    { this_also: {} },
    { works_with: {} },
    { arrays_of_objects: {} },
  ],
};

console.log(keysToCamel(o));