Work with the open source languages you love without the hassles of runtime management.

If JavaScript were detached from the client and server platforms, the pressure of being a monoculture would be lifted — the next iteration of the JavaScript language or run-time would no longer have to please every developer in the world, but instead could focus on pleasing a much smaller audience of developers who love JavaScript and thrive with it, while enabling others to move to alternative languages or run-times.

As to opinions about the shortcomings of the language itself, or the standard run-times, it’s important to realize that every developer has a different background, different experience, different needs, temperament, values, and a slew of other cultural motivations and concerns — individual opinions will always be largely personal and, to some degree, non-technical in nature.

As a simple example of a basic runtime system, the runtime system of the C language is a particular set of instructions inserted into the executable image by the compiler. Among other things, these instructions manage the process stack, create space for local variables, and copy function-call parameters onto the top of the stack. There are often no clear criteria for deciding which language behavior is considered inside the runtime system versus which behavior is part of the source program. For C, the setup of the stack is part of the runtime system, as opposed to part of the semantics of an individual program, because it maintains a global invariant that holds over all executions. This systematic behavior implements the execution model of the language

The ECMAScript standard does not include any input/output (I/O), such as networking, storage, or graphics facilities. In practice, the web browser or other runtime system provides JavaScript APIs for I/O.

runtimes (such as .NET and Unity)

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.