How to get a class from the constructor of an anonymous class inside it in JS

I have this situation in JS:

class Outer{
    constructor() {
        this.fruit = "orange";
        let inner = new this.Inner();
    }
    Inner = class{
        constructor() {
            // here
        }
    }
}
let outer = new Outer();

From the constructor of the class Inner, how can I get the current instance of Outer, as if this was used in the outer constructor?

Sure, I could pass the outer class as a parameter into the inner class' constructor, or put the outer class in a variable, but is there any other method?

You can use an IIFE to create the class and give it the current instance:

class Outer{
    constructor() {
        this.fruit = "orange";
        let inner = new this.Inner();
    }
    
    Inner = (instance => class{
        constructor() {
            console.log(instance instanceof Outer);
            console.log(instance.fruit);
        }
    })(this)
}
let outer = new Outer();

However, a more idiomatic approach is to accept the instance in the constructor of Inner. Then the class can be separated from Outer and Outer can expose a method that handles the construction of Inner which can create many instances of it:

class Inner {
    constructor(instance) {
        console.log(instance instanceof Outer);
        console.log(instance.fruit);
    }
}

class Outer{
    constructor() {
        this.fruit = "orange";
        let inner = this.makeInner();
    }
    
    makeInner() {
      return new Inner(this);
    }
}
let outer = new Outer();

const secondInnerInstance = outer.makeInner();

Or alternatively consider breaking the circular dependency between the two and introducing a factory to handle the more complex construction.