A guide to "delete this;" in JS classes

Redstone1080

Consider the following code:

class MyJSClass {
    constructor() {
        delete this;
    }
}

What would ‘delete’ do in this case? If you did

const myInstance = new MyJSClass();

would accessing myInstance produce an error?

Nope. It just pretty much creates an instance of an empty class.

However, static methods and fields still work, so if you want to create a class that is only usable through static methods and fields, you can use this method (although it probably isn't the best).

Here's the full code I tested this with:

class MyClass {
    static doesThisWork = false;
    constructor() {
        delete this;
    }
}
const myInstance = new MyClass();
console.log(myInstance.doesThisWork)
console.log(MyClass.doesThisWork)

Last edited by Redstone1080 (Oct. 9, 2022 22:34:22)

TrustyRoo

This is pretty logical, since you are creating the instance as a constant, even if you call the self destruct call in the class, it will not fully destroy itself because it is a constant at the end of the day and those cannot be destroyed before the end of the program. If it where not a constant, I would assume it would fully self destruct.

Redstone1080

TrustyRoo wrote:
(#2)
This is pretty logical, since you are creating the instance as a constant, even if you call the self destruct call in the class, it will not fully destroy itself because it is a constant at the end of the day and those cannot be destroyed before the end of the program. If it where not a constant, I would assume it would fully self destruct.

I tried it with let and var and I got the same result. So it isn't a constants thing.

Anyways, here's some more testing. This is a complete example that you can run anywhere and works.

Last edited by Redstone1080 (Oct. 9, 2022 23:52:29)

uwv

Redstone1080 wrote:
(#3)
TrustyRoo wrote:
(#2)
This is pretty logical, since you are creating the instance as a constant, even if you call the self destruct call in the class, it will not fully destroy itself because it is a constant at the end of the day and those cannot be destroyed before the end of the program. If it where not a constant, I would assume it would fully self destruct.
I tried it with let and var and I got the same result. So it isn't a constants thing.

Anyways, here's some more testing. This is a complete example that you can run anywhere and works.

this example is pretty flawed. you can't access static values in javascript using an instance, delete this doesn't really do anything. if you want to delete a value in javascript you have to set all references to either null or undefined

Redstone1080

uwv wrote:
Others wrote:
~snipped quotes~

Oh. I didn't know that. Thank you for this

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