I don't think that is true though. The spec make it clear that it only has access to a limited subset of the JS standard libraries and specially registered foreign functions:

> An asm.js module can take up to three optional parameters, providing access to external JavaScript code and data:

> - a standard library object, providing access to a limited subset of the JavaScript standard libraries;

> - a foreign function interface (FFI), providing access to custom external JavaScript functions; and

> - a heap buffer, providing a single ArrayBuffer to act as the asm.js heap.

From http://asmjs.org/spec/latest/#introduction:~:text=External%2...