Run event handler functions synchronously after a React state change - reactjs

Question

I know useEffect allows you to run a function after state is updated.
However, I want to run different logic after a state change based on which different event handler causes a state change.
Context
I have a Parent component that shows or hides a child DialogModal component based on the [isDialogShown, setIsDialogShown] = useState(false) in Parent.
When isDialogShown
The Parent passes setIsDialogShown and 2 event handler callbacks to DialogModal: onDismiss (which adds focus to some element) and onConfirm (which adds focus to another element).
When onDismiss or onConfirm on the DialogModal is pressed, setIsDialogShown(false) should run first to hide the DialogModal, then run the respective callbacks to focus on differing elements of the page.
const Parent = () => {
const [isDialogShown, setIsDialogShown] = useState(false);
// These need to run after Dialog is closed.
// In other words, after isDialogShown state is updated to false.
const focusOnElementA = () => { .... };
const focusOnElementB = () => { .... };
const handleDismiss = () => {
setIsDialogShown(false);
focusOnElementA() // Needs to run after state has changed to close the modal
}
const handleConfirm = () => {
setIsDialogShown(false);
focusOnElementB() // Needs to run after state has changed to close the modal
}
return (
<>
<Button onClick={() => { setIsDialogShown(true) }>Open dialog</Button>
<DialogModal
isOpen={isDialogShown}
onDismiss={handleDismiss}
onConfirm={handleConfirm}
/>
</>
)
}
What's the right pattern for dealing with this scenario?

Answer 1

I would use a separate state for the elements A and B to trigger them by in an additional effect. Enqueueing the toggle A/B state ensures the effect handles the update to call the focus A/B handles on the next render after the modal has closed.
const Parent = () => {
const [isDialogShown, setIsDialogShown] = useState(false);
const [toggleA, setToggleA] = useState(false);
const [toggleB, setToggleB] = useState(false);
useEffect(() => {
if (toggleA) {
focusOnElementA();
setToggleA(false);
}
if (toggleB) {
focusOnElementB();
setToggleB(false);
}
}, [toggleA, toggleB]);
const focusOnElementA = () => { .... };
const focusOnElementB = () => { .... };
const handleDismiss = () => {
setIsDialogShown(false);
setToggleA(true);
}
const handleConfirm = () => {
setIsDialogShown(false);
setToggleB();
}
return (
<>
<Button onClick={() => { setIsDialogShown(true) }>Open dialog</Button>
<DialogModal
isOpen={isDialogShown}
onDismiss={handleDismiss}
onConfirm={handleConfirm}
/>
</>
)
}

Answer 2

A slight difference to Drew's answer but achieved using the same tools (useEffect).
// Constants for dialog state
const DIALOG_CLOSED = 0;
const DIALOG_OPEN = 1;
const DIALOG_CONFIRM = 2;
const DIALOG_CANCELLED = 3;
const Parent = () => {
// useState to keep track of dialog state
const [dialogState, setDialogState] = useState(DIALOG_CLOSED);
// Set dialog state to cancelled when dismissing.
const handleDismiss = () => {
setDialogState(DIALOG_CANCELLED);
}
// set dialog state to confirm when confirming.
const handleConfirm = () => {
setDialogState(DIALOG_CONFIRM);
}
// useEffect that triggers on dialog state change.
useEffect(() => {
// run code when confirm was selected and dialog is closed.
if (dialogState === DIALOG_CONFIRM) {
const focusOnElementB = () => { .... };
focusOnElementB()
}
// run code when cancel was selected and dialog is closed.
if (dialogState === DIALOG_CANCELLED) {
const focusOnElementA = () => { .... };
focusOnElementA()
}
}, [dialogState])
return (
<>
<Button onClick={() => { setDialogState(DIALOG_OPEN) }}>Open dialog</Button>
<DialogModal
isOpen={dialogState === DIALOG_OPEN}
onDismiss={handleDismiss}
onConfirm={handleConfirm}
/>
</>
)
}

Answer 3

You should add another state for which element was triggered and then trigger the effect when the states change:
const [action, setAction] = useState('');
// ...code
const handleDismiss = () => {
setAction('dismiss');
setIsDialogShown(false);
}
const handleConfirm = () => {
setAction('confirm');
setIsDialogShown(false);
}
// Add dependencies to useEffect and it will run only when the states change
useEffect(() => {
if(!isDialogShown) {
if(action === 'dismiss') {
focusOnElementA()
} else {
focusOnElementB()
}
}
}, [action, isDialogShown])