Why doesn't JavaScript ES6 support multi-constructor classes?

Question

I want to write my Javascript class like below.

class Option {
    constructor() {
        this.autoLoad = false;
    }

    constructor(key, value) {
               


        

Answer 1

Guessing from your sample code, all you need is to use default values for your parameters:

class Option {
    constructor(key = 'foo', value = 'bar', autoLoad = false) {
        this[key] = value;
        this.autoLoad = autoLoad;
    }
}

Having said that, another alternative to constructor overloading is to use static factories. Suppose you would like to be able to instantiate an object from plain parameters, from a hash containing those same parameters or even from a JSON string:

class Thing {
    constructor(a, b) {
        this.a = a;
        this.b = b;
    }

    static fromHash(hash) {
        return new this(hash.a, hash.b);
    }

    static fromJson(string) {
        return this.fromHash(JSON.parse(string));
    }
}

let thing = new Thing(1, 2);
// ...
thing = Thing.fromHash({a: 1, b: 2});
// ...
thing = Thing.fromJson('{"a": 1, "b": 2}');

Answer 2

Use object.assigne with arguments with this

This={...this,...arguments}