Also interested. Looks like a lot of it is JS code written by hand. This is certainly readable code: https://ciechanow.ski/js/navarch.js
What are those?
{ // Start of block statement.
const foo = "a" + 2; // Only available inside block statement.
console.log(foo); // "a2"
} // End of block statement.
console.log(foo); // Uncaught ReferenceError: foo is not defined