This example presents four JavaScript practice problems embedded in an HTML page, focusing on array and object manipulation with population data for four U.S. states. The first problem uses `d3.mean()` to calculate and log the average population, demonstrating D3 v4’s array statistics method. The second problem attempts the same calculation manually with a `while` loop, but contains an intentional infinite loop and redundant addition. No SVG or visual output is rendered; results appear only in the browser’s developer console. The code relies on the D3 v4 library’s `mean()` function and standard JavaScript array traversal.