MobX Quick Start Guide

Completing the triad with reactions

When the fields are changed, we need to ensure that the values that have been entered are valid. Thus, validation is a side effect of entering values for the various fields. We know that MobX offers three ways in which you can handle this side effect, and they are autorun(), reaction(), and when(). Since validation is an effect that should be performed every time a field changes, when(), a one-time only effect, can be ruled out. That leaves us with reaction() and autorun(). Typically, a form will only validate when a field has actually changed. This means the effect needs to trigger only after a change.

That narrows down our choice to reaction(<tracking-function>, <effect-function>), as that's the only ...