MobX Quick Start Guide

Observing the state changes

Observables alone cannot make an interesting system. We also need their counterparts, the observers. MobX gives you three different kinds of observers, each tailor-made for the use cases you will encounter in your application. The core observers are autorun, reaction, and when. We will look at each of them in more detail in the next chapter, but let's introduce autorun for now.

The autorun API takes a function as its input and executes it immediately. It also keeps track of the observables that are used inside the passed-in function. When these tracked observables change, the function is re-executed. What is really beautiful and elegant about this simple setup is that there is no extra work required to track observables ...