mutation notifier

a.js

function MutationNotifier (
  original,
  event,
  args,
  deep,
  path
) {
  if (args == null) { args = {}; }
  if (deep == null) { deep = false; }
  if (path == null) { path = ''; }
  let init = true
  const proxy = new Proxy({}, {
    set(target, property, value, receiver) {
      if (value !== target[property]) {
        const payload = R.mergeRight(args, {
          property,
          path,
          value,
          oldValue: R.clone(target[property])
        });
        if (!init) {
          process.nextTick(() => emit(event, payload));
        }
        if (deep && L.isObjectLike(value)) {
          value = MutationNotifier(value, event, args
          , true, `${path}.${property}`.replace(/^\./, ''));
        }
      }
      return Reflect.set(target, property, value, receiver);
    },
    deleteProperty(target, property) {
      const payload = R.mergeRight(args, {
        property,
        value: undefined,
        oldValue: R.clone(target[property])
      });
      if (!init) {
        process.nextTfick(() => emit(event, payload));
      }
      return Reflect.deleteProperty(target, property);
    }
  }
  );

  L.assign(proxy, original)
  init = false
  return proxy
};