Inheritance

Front 1

What does "class Child extends Parent" mean?

Back 1

That means
Child.prototype.__proto__ == Parent.prototype

Front 2

What is the field initialization order for base/derived class?

Back 2

The class field is initialized:Before constructor for the base class (that doesn’t extend anything),

Immediately after super() for the derived class.

Front 3

How to call a method from parent class?

Back 3

super.method(...)

Front 4

What effect has constructor internal property [[ConstructorKind]] with value "derived"

Back 4

That label affects its behavior with new.When a regular function is executed with new, it creates an empty object and assigns it to this.But when a derived constructor runs, it doesn’t do this. It expects the parent constructor to do this job.So a derived constructor must call super in order to execute its parent (base) constructor, otherwise the object for this won’t be created. And we’ll get an error.

Front 5

if a class extends another class and has no constructor, then the following “empty” constructor is generated:

Back 5

class Rabbit extends Animal { // generated for extending classes without own constructors constructor(...args) { super(...args); }}

Front 6

What should constructors in inheriting classes must call first?

Back 6

Constructors in inheriting classes must call super(...), and (!) do it before using this.

Front 7

Which field values does always use parent constructor?

Back 7

the parent constructor always uses its own field value, not the overridden one

Front 8

animal.eat

.[[HomeObject]] == ?

Back 8

animal

Front 9

What syntax should be used for objects in order that calling super.method() was working?
"method()" or "method: function()"

Back 9

for objects, methods must be specified exactly as method(), not as "method: function()"