This example demonstrates how to manipulate JavaScript arrays using both vanilla methods and the D3 library. It shows common operations like range creation, filtering, sorting, mapping, and reducing, with results logged to the console. The code reconstructs D3’s `range` function, sorts objects by key using `d3.ascending`, and transforms an array of entries into a dictionary via `reduce`. The final output visualizes array mutation and data reshaping in a step-by-step console sequence.