4. The Elemelons

function arr() {
    class Melon {
        constructor(weight, melonSort) {
            if (new.target === Melon)
                throw new TypeError(`Abstract class cannot be instantiated directly`);
            this.weight = weight;
            this.melonSort = melonSort;
        }
    }
    class Watermelon extends Melon {
        constructor(weight, melonSort) {
            super(weight, melonSort)
        }
        get elementIndex() {
            return Number(this.weight) * Number(this.melonSort.toString().length)
        }
        toString() {
            return `Element: Water\nSort: ${this.melonSort}\nElement Index: ${this.elementIndex} `
        }
    }
    class Firemelon extends Melon {
        constructor(weight, melonSort) {
            super(weight, melonSort)
        }
        get elementIndex() {
            return Number(this.weight) * Number(this.melonSort.toString().length)
        }
        toString() {
            return `Element: Fire\nSort: ${this.melonSort}\nElement Index: ${this.elementIndex} `
        }
    }
    class Earthmelon extends Melon {
        constructor(weight, melonSort) {
            super(weight, melonSort)
        }
        get elementIndex() {
            return Number(this.weight) * Number(this.melonSort.toString().length)
        }
        toString() {
            return `Element: Earth\nSort: ${this.melonSort}\nElement Index: ${this.elementIndex} `
        }
    }
    class Airmelon extends Melon {
        constructor(weight, melonSort) {
            super(weight, melonSort)
        }
        get elementIndex() {
            return Number(this.weight) * Number(this.melonSort.toString().length)
        }
        toString() {
            return `Element: Air\nSort: ${this.melonSort}\nElement Index: ${this.elementIndex} `
        }
    }
    class Melolemonmelon extends Melon {
        constructor(weight, melonSort) {
            super(weight, melonSort);
            this.element = [`Water`, `Fire`, `Earth`, `Air`]
        }
        get elementIndex() {
            return Number(this.weight) * Number(this.melonSort.toString().length)
        }
        morph() {
            let a = this.element.shift();
            this.element.push(a)
        }
        toString() {
            return `Element: ${this.element[0]}\nSort: ${this.melonSort}\nElement Index: ${this.elementIndex} `
        }
    }
    return {Melon, Watermelon, Firemelon, Earthmelon, Melolemonmelon}
}