If you want a reference to the global object that works in any context, you can read this from a directly-called function. const global = (function() {return this})();. This evaluates to window in the browser, self in a service worker and global in nodejs.

But what if you want a runtime with some features? what if you want, say, a runtime with very powerful coroutine support? The answer is: you write Go.

Notably, LLVM and JVM are by far the most prominent targets in this scenario: they’re both open-source and well-documented targets that provide a ton of firepower, and there frankly aren’t a ton of other options.

The environment in which an executing program operates is sometimes called its “runtime environment,” or just runtime

When you write a C program, your runtime environment is very bare – the C compiler turns your code into machine code and really adds very little beyond that. When you write a Python program, however, the runtime is rich: the interpreter is the thing that’s actually running, and does things like managing your memory and doing function dispatch for you.

Notable early examples of runtime systems are the interpreters for BASIC and Lisp.