Agreed, but as for Python, it doesn't have to run in both CLI and the browser, where both are entirely different environments. You don't need to transpile-and-

Agreed, but as for Python, it doesn't have to run in both CLI and the browser, where both are entirely different environments. You don't need to transpile-and-typecheck from Python-with-types to Python-you-can-run. And yet, there are enough complaints about trying to get other people's Python to run on one's own machine, even in this very comment thread.