This example demonstrates loading a heart failure prediction dataset from a CSV file via a file input, then displaying its contents as a formatted JSON object. The visualization initially fetches `heart.csv` using D3's `fetch` and `csvParse` functions, converting numeric columns to numbers. Users can subsequently load their own CSV file, which is read using the `FileReader` API and parsed by `d3.csvParse`, updating the displayed state. The code relies on D3's `select`, `selectAll`, and `join` operations to render the data.