JSON extender that works even with stringified son

extender.js

/**
 * clone a string or object
 * @param {object|string} input - the input to the function.
 * @return {object|string} output - the cloned data.
 */
const clone = function clone(input) {
  if (typeof input === 'string') return input;
  return Object.assign({}, input);
};

/**
 * extend a string or object
 * [TODO if input is array]
 * @param {object|string} input - the input to the function.
 * @param {object} toExtend - toExtend.
 * @return {object|string} output - the extended data.
 */
const extend = function extend(input, toExtend) {
  if (typeof input === 'object') {
    return Object.assign(input, toExtend);
  }
  if (typeof toExtend !== 'object' || toExtend === null) {
    return input;
  }
  return `${input.slice(0, -1)},${JSON.stringify(toExtend).slice(1)}`;
};