Stacked Horizontal Bar Chart

Stacked horizontal bar chart showing the cumulative population of different age groups per state in the U.S. (2018). Adapted from

The (async () => { ... })() bit is a so-called Immediately Invoked Function Expression, which is just a way to define a function and run it immediately without having to give it a name. It is used here to contain all logic that depends on asynchronous operations like fetching datasets.