These can only be subclassed, not constructed on their own or called as a function.

unconstructable-uncallable-constructors.js

// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/new.target

class Special {
	constructor() {
		if (new.target === Special)
			throw new TypeError("Failed to construct 'Special': Illegal constructor");
	}
}

function AlsoSpecial() {
	if (new.target === AlsoSpecial)
		throw new TypeError("Failed to construct 'AlsoSpecial': Illegal constructor");
	else if (new.target === undefined)
		throw new TypeError("Failed to construct 'AlsoSpecial': Please use the 'new' operator, this special object constructor cannot be called as a function.");
}

class NotSoSpecial extends Special {}
function AlsoNotSoSpecial() {
	// If you drop the sub-class argument, this will fail.
	return Reflect.construct(AlsoSpecial, arguments, AlsoNotSoSpecial);
}
AlsoNotSoSpecial.prototype = Object.create(AlsoSpecial.prototype);

// All of these will fail
try { new Special() } catch(error) { console.error(error); }
try { Special() } catch(error) { console.error(error); } // Built-in error
try { new AlsoSpecial() } catch(error) { console.error(error); }
try { AlsoSpecial() } catch(error) { console.error(error); }

new NotSoSpecial(); // Works
new AlsoNotSoSpecial(); // Also, works