Properties not passed when calling super() in derived class constructor

[andriichern]

I have two objects

class Base extends ObjectModel({ id: String, type: String, required: Boolean }) { constructor(obj, type) { super({ // property initialization }); } }

and

class Derived extends Base.extend({ values: Array }) { constructor(obj) { super({ ...obj, values: // property initialization code }, 'typeStr'); } }

The problem is when I call super() inside Derived class constructor second parameter in Base constructor is always undefined. Tried different call variants - got no real value, always undefined

[sylvainpolletvillard]

Sorry for the delay.

I rewrote your code with more detailed steps:

const BaseModel =  ObjectModel({ id: String, type: String, required: Boolean })

class Base extends BaseModel { 
   constructor(obj, type) {
     super({ ...obj, type }); 
   }
}

const DerivedModel = Base.extend({ values: Array })

class Derived extends DerivedModel { 
   constructor(obj) { 
       super({ ...obj, values: [] }, 'typeStr');
   }
}

With this code, the Derived class extends an ObjectModel (DerivedModel). So when calling super, you invoke the DerivedModel constructor, not the Base constructor. DerivedModel is an ObjectModel so its constructor takes only one argument: an object. That's why second argument is always undefined.

The solution is to rewrite constructors so that they all match the same signature, that is, a single object as argument. Personnally, I consider consistent constructor signatures to be a good practice.