Returns false if the function is an ES6 class (non-emulated!), async,
generator, or async generator function. Returns true for regular, arrow, and
bound regular functions.
Note: a function can return a promise or generator or implement a class, and
yet still not be an async function, generator function, or native class.
This function doesn't detect/reject any emulated versions of those things,
only native-to-the-engine async/generator functions and classes. (It also
returns false for CallableObject instances, or similarly-created
function subclasses.)
Is the given value a plain synchronous function?
Returns false if the function is an ES6 class (non-emulated!), async, generator, or async generator function. Returns true for regular, arrow, and bound regular functions.
Note: a function can return a promise or generator or implement a class, and yet still not be an async function, generator function, or native class. This function doesn't detect/reject any emulated versions of those things, only native-to-the-engine async/generator functions and classes. (It also returns false for CallableObject instances, or similarly-created function subclasses.)