Mobx Reaction Control

What is this?

This is a simple Mobx wrapper that enables you to control Mobx reactions. Let me show you:

import { makeAutoObservableWithControl } from "mobx-reaction-control";
import { autorun } from "mobx";

const obj = makeAutoObservableWithControl({ a: 1 });

autorun(() => {
  console.log("Change", obj.a);
}); // Change 1

obj.a = 2; // Change 2

obj.pauseKey("a");

obj.a = 3; // Nothing, reaction was not triggered

console.log(obj.a); // 3, changes are still made

obj.resumeKey("a");

obj.a = 4; // Change 4

That's basically it, however the wrapper adds two more methods: pauseAll and resumeAll, if you want to pause all reactions on an object.

Here's the implemented interface:

type IReactionControl<T> = {
  pauseKey: (...keys: (keyof T)[]) => void;
  resumeKey: (...keys: (keyof T)[]) => void;
  pauseAll: () => void;
  resumeAll: () => void;
} & T;

There's one more feature that could come in handy, namely unfreeze reactions. Let me show you:

const obj = makeAutoObservableWithControl({ a: 1 }, undefined, undefined, true); // I added one more argument to the vanilla Mobx interface

autorun(() => {
  console.log("Change", obj.a);
}); // Change 1

obj.pauseKey("a");

obj.a = 2;

obj.resumeKey("a"); // Change 2, reactions are triggered if there were any changes to the "frozen" keys

Warning

The functions exposed by this package are not recursive. You won't be able to control the behavior of nested objects. Moreover, TypeScript typings won't work correctly if you do this:

const obj = { a: 1 };
makeAutoObservableWithControl(obj);

instead of this:

const obj = makeAutoObservableWithControl({ a: 1 });

Why would I use it?

I developed this package for myself to simplify the following scenario:

I have a Mobx-based form and a reaction that triggers a server request on any form model change. In most cases it works fine, but I wanted the ability to "batch" the changes without significant changes to the existing form logic. With this package all I need to do is add formModel.pauseAll() and formModel.resumeAll() invocations.