Why is the data undefined if it s passing data

Question

With the help of code can you tell me Why is the data undefined if it's passing data?

Answer 1

It’s likely due to one of these precise issues:

Data Initialization Timing: The data array might not be fully initialized when the virtualizer renders. In your code, data is created synchronously with Array.fill().map(), which should work, but if it’s derived from an async source (e.g., API call) and not yet resolved, it’ll be undefined. Fix: Ensure data is defined before rendering, e.g., use a loading state:

if (!data) return <div>Loading...</div>;

Incorrect Indexing: The virtualizer uses row.index and col.index to access data[row.index][col.index]. If data is not a 2D array or has fewer rows/columns than rowCount/colCount, you’ll get undefined. Fix: Verify data matches dimensions:

const data = Array(rowCount).fill().map(() => Array(colCount).fill(''));

Scope or Reference Issue: If data is passed as a prop or state and updated after the initial render, the virtualizer might reference an outdated or uninitialized version. Fix: Ensure data is stable and passed correctly, e.g.:

const VirtualGrid = ({ data }) => { ... };

Rendering Before Virtualization: The virtualizer might render before calculating virtual items, accessing data out of bounds. Fix: Guard against invalid indices:

{data[row.index] && data[row.index][col.index]}