Bar Chart I
A simple bar chart displays a single array of seven numeric values as horizontally aligned rectangular bars. The bars are rendered as styled HTML `div` elements, with their widths proportional to the data values via a linear `d3.scale.linear` mapping values to pixel lengths. The chart uses D3 v3’s data join (`selectAll`, `data`, `enter`) to append the bars, and each bar is labeled with its corresponding number inside a colored, right-aligned text block against a black background. The example is a direct implementation of the classic "Let’s Make a Bar Chart" tutorial.