Define a new Mixin

You can use the Mixin decorator to define a new mixin. Amongst other things, the decorator will enable support for instanceof checks. See instanceof Operator for additional information.

import { Mixin } from "@aedart/support/mixins";

export const RectangleMixin = Mixin((superclass) => class extends superclass {
    length = 0
    width = 0;
    
    area() {
        return this.length * this.width;
    }
});

Constructor

If you need to perform initialisation logic in your mixins, then you can do so by implementing a class constructor. When doing so, it is important to invoke the parent constructor via super() and pass on eventual arguments.

import { Mixin } from "@aedart/support/mixins";

export const RectangleMixin = Mixin((superclass) => class extends superclass {
    
    constructor(...args) {
        super(...args); // Invoke parent constructor and pass on arugments!
        
        // Perform your initialisaiton logic...
    }
    
    // ...remaining not shown...
});