Blog: Debugging Duplicate IDs in React Components

Imagine you have two child components, each rendering a list of switches:

First Component (List A):

const [featuresList, setFeaturesList] = useState([
    { title: 'Check for missing information', checked: true },
    { title: 'Scan for broken links', checked: true },
]);

<Switch>
    <SwitchInput
        type="checkbox"
        id={`adminNotificationFeatures-${index}`}
        checked={data.checked}
        onChange={() => handleChange(index)}
    />
    <SwitchLabel htmlFor={`adminNotificationFeatures-${index}`}></SwitchLabel>
</Switch>;

Second Component (List B):

const [featuresLists, setFeaturesLists] = useState([
    { title: 'Login', checked: true },
    { title: 'Logout', checked: true },
]);

<Switch>
    <SwitchInput
        type="checkbox"
        id={`adminNotificationFeatures-${index}`}
        checked={data.checked}
        onChange={() => handleChange(index)}
    />
    <SwitchLabel htmlFor={`adminNotificationFeatures-${index}`}></SwitchLabel>
</Switch>;

While everything appears fine, the id for both lists will overlap (adminNotificationFeatures-0, adminNotificationFeatures-1, etc.).

This causes a conflict, as the browser associates multiple elements with the same id. Clicking on a switch in one list may trigger unintended behavior in the other.

To fix this, make sure that each id is unique across the entire application. You can prepend a unique identifier for each list.

Updated First Component (List A):

<Switch>
    <SwitchInput
        type="checkbox"
        id={`featuresList-${index}`}
        checked={data.checked}
        onChange={() => handleChange(index, 'featuresList')}
    />
    <SwitchLabel htmlFor={`featuresList-${index}`}></SwitchLabel>
</Switch>;

Updated Second Component (List B):

<Switch>
    <SwitchInput
        type="checkbox"
        id={`featuresLists-${index}`}
        checked={data.checked}
        onChange={() => handleChange(index, 'featuresLists')}
    />
    <SwitchLabel htmlFor={`featuresLists-${index}`}></SwitchLabel>
</Switch>;

To ensure each component’s state updates independently, pass a listType parameter to differentiate the lists:

const handleChange = (index, listType) => {
    if (listType === 'featuresList') {
        setFeaturesList(prev =>
            prev.map((item, i) => (i === index ? { ...item, checked: !item.checked } : item))
        );
    } else if (listType === 'featuresLists') {
        setFeaturesLists(prev =>
            prev.map((item, i) => (i === index ? { ...item, checked: !item.checked } : item))
        );
    }
};

HTML attributes like id must be unique within a page. React is declarative, but the DOM still follows this rule. Assigning duplicate id values creates conflicts when associating labels with inputs or processing DOM-based events.

1. Avoid Overlapping Indexes: Use unique prefixes for dynamic id values.
2. Use Context or Props: Pass a unique identifier for each component if needed.
3. Test Behavior: Verify components in isolation to catch issues early.