deepClone.js

// a strictly educational deep clone attempt/approach.

function exposeInternalyType(value) {
  return Object.prototype.toString.call(value);
}

function isRegExp(value) {
  return exposeInternalyType(value) === '[object RegExp]';
}
function isDate(value) {
  return exposeInternalyType(value) === '[object Date]';
}

function deepClone(value) {
  let clone = value;

  if (value && typeof value === 'object') {
    if (isRegExp(value)) {

      clone = new RegExp(value);

    } else if (isDate(value)) {

      clone = new Date(value);

    } else if (Array.isArray(value)) {

      // recursive cloning.
      clone = value.map(deepClone);

    } else {

      clone = Object.create(Object.getPrototypeOf(value));

      const entryList = [
        ...Object.getOwnPropertyNames(value),
        ...Object.getOwnPropertySymbols(value),
      ]
      .map(key =>
        [key, Reflect.getOwnPropertyDescriptor(value, key)]
      );

      entryList.forEach(([key, descriptor]) => {
        const { writable, enumerable, configurable } = descriptor;
        const isPublicValue = Object.hasOwn(descriptor, 'value');

        if (writable && enumerable && configurable && isPublicValue) {

          // recursive cloning.

          // // clone[key] = deepClone(value[key]);
          clone[key] = deepClone(descriptor.value);          

        } else if (isPublicValue) {

          // recursive cloning.

          // // Reflect.defineProperty(clone, key, { descriptor, value: deepClone(value[key]) });
          Reflect.defineProperty(clone, key, { descriptor, value: deepClone(descriptor.value) });

        } else {
          // assume at least a read-only, `get` protected, value.

          // recursive cloning.
          Reflect.defineProperty(clone, key, { descriptor, value: deepClone(value[key]) });

          // or any other handling of how to clone a protected value.
        }
      });
    }
  } else if (typeof value === 'function') {

    clone = Function.prototype.bind.call(value);

    // or any other handling of how to (not) clone a function.
  }
  return clone;
}