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+---
+title: Put Interaction Logic in Event Handlers
+impact: MEDIUM
+impactDescription: avoids effect re-runs and duplicate side effects
+tags: rerender, useEffect, events, side-effects, dependencies
+---
+
+## Put Interaction Logic in Event Handlers
+
+If 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.
+
+**Incorrect (event modeled as state + effect):**
+
+```tsx
+function Form() {
+  const [submitted, setSubmitted] = useState(false);
+  const theme = useContext(ThemeContext);
+
+  useEffect(() => {
+    if (submitted) {
+      post("/api/register");
+      showToast("Registered", theme);
+    }
+  }, [submitted, theme]);
+
+  return <button onClick={() => setSubmitted(true)}>Submit</button>;
+}
+```
+
+**Correct (do it in the handler):**
+
+```tsx
+function Form() {
+  const theme = useContext(ThemeContext);
+
+  function handleSubmit() {
+    post("/api/register");
+    showToast("Registered", theme);
+  }
+
+  return <button onClick={handleSubmit}>Submit</button>;
+}
+```
+
+Reference: [Should this code move to an event handler?](https://react.dev/learn/removing-effect-dependencies#should-this-code-move-to-an-event-handler)