This bar chart displays the top 10 most populous countries using United Nations World Population Prospects 2019 data. The visualization uses D3.js v4 to render SVG rectangles, with `d3.csv` loading the dataset and a custom React hook managing the data state. The chart employs an ordinal y-scale for country categories and a linear x-scale for population values, with tooltips showing exact figures. The code also includes a separate D3.js example using an array of numbers, demonstrating both React-integrated and standalone D3 approaches to bar chart creation.