A bar chart displays monthly revenue and profit data from a JSON file, toggling between the two metrics every two seconds. Built with React and D3 v5, the visualization uses a band scale for months and linear scales for values, with axis transitions via `d3.transition()`. The update pattern joins data to SVG rectangles, animating height, position, and fill color as bars swap between tomato (revenue) and green (profit), while newly entered bars grow from the baseline.