Do we want to trust a transpiler when dealing with cryptography code? Building encryption that is resistant to side-channel attacks requires knowledge of the ex

Do we want to trust a transpiler when dealing with cryptography code? Building encryption that is resistant to side-channel attacks requires knowledge of the execution environment. When the environment changes drastically then many assumptions about the strength of the code need to be reevaluated. Plus the usual caveat about trusting code that is downloaded from the internet. Although this also has a use in iPhone & Android apps that are written in Javascript. This lets you have encryption without using native code. Somewhat tangential, but is Emscripten generated code being used in any production web apps? I don't think I've ever seen it for anything other then proof-of-concept demos. (Answering my own question, doesn't Unreal Engine use Emscripten?)