Create a class that is callable and with a callable constructor

Question

Such as with the Boolean object. How can a class be made to have a static method that can be called just by calling the class itself, but also have a normal callable constructor?

When a function is called as a constructor, the value of `this` is a new object that has the function as its constructor. If a function doesn't see that being the case, it can behave differently than it would if called as a constructor. — Pointy, Dec 05 '22 at 02:08
@Pointy That's not what I mean, they would be two separate methods — Aidan, Dec 05 '22 at 02:13
It is not at all clear what you're talking about. There's only one `Boolean` function. It can be used as a constructor or as a function. There are not two of them, just one. — Pointy, Dec 05 '22 at 02:20
@Pointy See my answer, essentially I was looking for the ability to write different behavior depending on if the reference was called a constructor or not, such as with `Boolean` — Aidan, Dec 05 '22 at 02:32
I'm glad you found a solution, but please note that what you ended up doing is pretty much exactly what I said in the original comment. — Pointy, Dec 05 '22 at 02:33
FWIW, functions in JavaScript can be *callable* or *constructable* or both. "Normal" function definitions create a functions that are both. Functions/constructors created via `class` are only constructable and arrow functions (and methods I believe (not sure)) are only callable. — Felix Kling, Dec 05 '22 at 10:29

score 0 · Answer 1 · answered Dec 05 '22 at 02:12

0

If you need just shortname to get you method in special place you can create scope and put method in variable.

Example:

// GLOBAL SCOPE

{
// create local scope
// create variable
const methodByClass = myObject.getData;

// use it method
methodByClass();
}

Hope it helpful for you

answered Dec 05 '22 at 02:12

gureenkov56

172
3

No, this isn't what I meant. Instead, I am wanting to have a single reference that is both callable, and has a constructor – Aidan Dec 05 '22 at 02:15

score 0 · Answer 2 · answered Dec 05 '22 at 02:31

0

function MyClass(x) {
  if (new.target) {
    this.x = x * 2
   } else {
    return x * 2;
   }
  }
  
console.log( MyClass(3) )
console.log( new MyClass(4) )

I found the answer from this question

answered Dec 05 '22 at 02:31

Aidan

413
3
22

Right, exactly, and there's only one function as I said originally in my comment. – Pointy Dec 05 '22 at 02:32

score 0 · Answer 3 · answered Dec 05 '22 at 03:30

You can also create this type of construct as a function, setting properties on instances using this:

function MyBool(value) {
    this.value = !!value

    return !!value
}

console.log(MyBool(1))
console.log(new MyBool(1))

This is also the way classes were created in JS before the class keyword was included in the language.

Create a class that is callable and with a callable constructor

3 Answers3