Function isGenericFunction

Detects whether the passed value is a generic (unspecific/non-specific) function ...

• either a good old ES3 function,
• or a non-async arrow function expression.
• or either a non-async and non-generator concise method (shorthand function definition).

Thus, the following specific (non-generic) function types are excluded ...

• class constructor functions,
• any generator function,
• any async function variant,
• extended Function types,
• built-in constructor functions,
• Web Api constructor functions.