This example demonstrates the foundational steps of creating and styling SVG elements using plain JavaScript. It creates an SVG container that fills the entire browser window using the `document.createElementNS` API with the SVG namespace. The code then appends a rectangle with a fixed width of 100 pixels and height of 50 pixels, filling it with black via the `setAttribute` method. The example relies entirely on native browser APIs—no external libraries such as D3 or React—though the metadata notes the framework as React, which is not used in the visible code.