instanceof-with-sugar.js

class MyClass {
    static [Symbol.hasInstance](lho) {
        console.log('with-sugar: is', lho, 'an array?');
        return Array.isArray(lho);
    }
}

console.log([] instanceof MyClass); // true
console.log('my string' instanceof MyClass); // false

isntanceof-without-sugar.js

const MyClass = function() {};

Object.defineProperty(MyClass.prototype.constructor, Symbol.hasInstance, {
	value: function(lho) {
		console.log('without-sugar: is', lho, 'an array?');
		return Array.isArray(lho);
	}
});


console.log([] instanceof MyClass); // true
console.log('my string' instanceof MyClass); // false