The answer to the question is something an Arrow or Class or regular Function

isArrowOrFunctionOrClass.js

'use strict';

const myArrow = () => {};
const myFn = function () {};

class MyClass {};

const isArrowFunction = (fn) => {
	if (typeof fn !== 'function') {
		return false;
	}
	if (fn.prototype !== undefined) {
		return false;
	}
	return true;
};

const isRegularFunction = (fn) => {
	if (typeof fn !== 'function') {
		return false;
	}
	if (typeof fn.prototype !== 'object') {
		return false;
	}
	if (fn.prototype.constructor !== fn) {
		return false;
	}
	return Object.getOwnPropertyDescriptor(fn, 'prototype').writable === true;
};

const isClass = (fn) => {
	if (typeof fn !== 'function') {
		return false;
	}
	if (typeof fn.prototype !== 'object') {
		return false;
	}
	if (fn.prototype.constructor !== fn) {
		return false;
	}
	return Object.getOwnPropertyDescriptor(fn, 'prototype').writable === false;
};


console.log('--- arrow ---')
console.log('is arrow : ', isArrowFunction(myArrow));	// true
console.log('function : ', isRegularFunction(myArrow));	// false
console.log('is class : ', isClass(myArrow));		// false

console.log('--- function ---')
console.log('is arrow : ', isArrowFunction(myFn));	// false
console.log('function : ', isRegularFunction(myFn));	// true
console.log('is class : ', isClass(myFn));		// false

console.log('--- class ---')
console.log('is arrow : ', isArrowFunction(MyClass));	// false
console.log('function : ', isRegularFunction(MyClass));	// false
console.log('is class : ', isClass(MyClass));		// true

debugger;