What practical use is a Boolean object in Javascript?

Question

Given that in JavaScript

console.log("var F=new Boolean(false)")
console.log("( F != (F==false))",(( F != (F==false)) ? "TRUE" : "false"));
console.log("(!F != (F==false))",((!F != (F==false)) ? "TRUE" : "false"));

prints:

( F != (F==false)) TRUE
(!F != (F==false)) TRUE

which means that Boolean objects are not dop-in substitutes for a boolean primitive in typical conditions like:

if(someBoolean) ...  // always true
if(!someBoolean) ... // always false

And that JavaScript's Set and Map collections permit any type, including primitives.

What use are Boolean objects, in particular; and the objects representing other primitive types in general, since they have all sort of weird in consistencies associated with them?

Note: I am specifically asking what are the use-cases (if any), not how they are different from their primitive counterparts.

Answer 1

Boolean objects are just objects, and thus are truthy.

console.log(!!new Boolean(true)); // true
console.log(!!new Boolean(false)); // true

Boolean objects exist because this way you can add methods to Boolean.prototype and use them on primitive booleans (which will be wrapped into booolean objects under the hood).

Boolean.prototype.foo = function() {
  console.log("I'm the boolean " + this + "!!");
};
true.foo();
false.foo();

They are also useful when you want to store properties in a boolean.

var wrappedBool = new Boolean(false);
wrappedBool.foo = "bar";
console.log("Property foo: ", wrappedBool.foo); // "bar"
console.log("Unwrapped bool: ", wrappedBool.valueOf()); // false

But that's not recommended.