This example demonstrates common JavaScript array manipulation techniques, including `map`, `filter`, `reduce`, and custom sorting, using both native methods and D3’s `ascending` and `descending` helpers from d3-array. The code creates a range of numbers, filters for even values, transforms objects, and sorts an array of numeric and key–value entries. It shows how `reduce` can aggregate values or build an object from array entries. The visualization is a bare HTML page with no rendered graphics, focusing instead on console output for learning array operations.