This example demonstrates how to build a bar chart using D3.js v7, displaying either population data by country or monthly credit totals. The visualization renders as SVG, with bar orientation switchable between horizontal and vertical layouts through a scaleBand and scaleLinear pairing. The code loads data from CSV or JSON files via d3.csv and d3.json, then processes transactions to aggregate monthly credits. A class-based structure manages the chart dimensions, scales, and data mapping.