an example of Unbind via new keyword

AnotherUnbind.js

'use strict';
function anotherBeBound () {
	debugger;
	this.b = this.a;
	if (!new.target) {
		return this;
	}
};
anotherBeBound.prototype.a = 2;

const anotherBound = anotherBeBound.bind({a: 1});

console.log((anotherBound()).b);	// 1
console.log((new anotherBound).b);	// 2

Unbind.js

'use strict';

function toBeBound () {
	return this.a;
};
toBeBound.prototype.a = 2;

const bound = toBeBound.bind({a: 1});

console.log(bound());		// 1
console.log((new bound).a); // 2

Here is another example from:
https://gist.github.com/tadger/4572db07fa81f92d2cfd4bc4bedfeffd

  var unbind = Function.bind.bind(Function.bind);

  function instantiate(constructor, args) {
    return new (unbind(constructor, null).apply(null, args));
  }