1---
2title: Put Interaction Logic in Event Handlers
3impact: MEDIUM
4impactDescription: avoids effect re-runs and duplicate side effects
5tags: rerender, useEffect, events, side-effects, dependencies
6---
7 
8## Put Interaction Logic in Event Handlers
9 
10If a side effect is triggered by a specific user action (submit, click, drag), run it in that event handler. Do not model the action as state + effect; it makes effects re-run on unrelated changes and can duplicate the action.
11 
12**Incorrect (event modeled as state + effect):**
13 
14```tsx
15function Form() {
16  const [submitted, setSubmitted] = useState(false)
17  const theme = useContext(ThemeContext)
18 
19  useEffect(() => {
20    if (submitted) {
21      post('/api/register')
22      showToast('Registered', theme)
23    }
24  }, [submitted, theme])
25 
26  return <button onClick={() => setSubmitted(true)}>Submit</button>
27}
28```
29 
30**Correct (do it in the handler):**
31 
32```tsx
33function Form() {
34  const theme = useContext(ThemeContext)
35 
36  function handleSubmit() {
37    post('/api/register')
38    showToast('Registered', theme)
39  }
40 
41  return <button onClick={handleSubmit}>Submit</button>
42}
43```
44 
45Reference: [Should this code move to an event handler?](https://react.dev/learn/removing-effect-dependencies#should-this-code-move-to-an-event-handler)
46