The reason they use JavaScript is because it's known by many and the examples can be tried without downloading/having an additional compiler. There are at least

The reason they use JavaScript is because it's known by many and the examples can be tried without downloading/having an additional compiler. There are at least two dozen concepts on the list there - the value of illustrating new concepts for some with a known quantity far outweighs the downsides of having to start with a fresh environment. I will say though for the exact cases you mention, they probably should be clear why this isn't exactly the concept as described.