How do you check the difference between an ECMAScript 6 class and function?

Question

In ECMAScript 6 the typeof of classes is, according to the specification, \'function\'.

However also according to the specification you are

Answer 1

I think the simplest way to check if the function is ES6 class is to check the result of .toString() method. According to the es2015 spec:

The string representation must have the syntax of a FunctionDeclaration FunctionExpression, GeneratorDeclaration, GeneratorExpression, ClassDeclaration, ClassExpression, ArrowFunction, MethodDefinition, or GeneratorMethod depending upon the actual characteristics of the object

So the check function looks pretty simple:

function isClass(func) {
  return typeof func === 'function' 
    && /^class\s/.test(Function.prototype.toString.call(func));
}