I got a problem with calling super inside of the child static method.
const _todos = [];
class Todo {
constructor(title) {
this.title = title;
this.id = Math.round(Math.random() * 100);
_todos.push({title, id: this.id});
console.log(`Todo ID: ${this.id}. DONT FORGET IT!`);
}
static TodoerVersion = '1.8';
static removeTodo(id) {
const todoIndex = _todos.findIndex(t => t.id == id);
_todos.splice(todoIndex, 1);
}
}
class TodoV2 extends Todo {
static addTodo(title) {
super(title);
}
static addDescription(todo, description) {
todo.description = description;
}
static TodoerVersion = '2.0';
};
new TodoV2("play guitar");
Why does it not work?
But if i call super in normal method, it would works just fine.
super is only callable within the constructor function of a class.
Two answers for you:
The question you actually asked.
What I think you should do instead. :-)
JavaScript is very special in this regard: this has meaning in static methods (as long as you call them correctly, e.g. TodoV2.addTodo("title")): it's the constructor function you called the static method on. And a subclass constructor function inherits from its superclass constructor function (yes, really). So you can access the constructor function for the parent class using Object.getPrototypeOf(this) in the static method:
// This is something unusual that JavaScript actually does support
static addTodo(title) {
const ctor = Object.getPrototypeOf(this);
return new ctor(title);
}
To handle the case where the user may have called addTodo in a way that doesn't set this, you might do something like this to default to TodoV2 if this is undefined:
static addTodo(title) {
const ctor = Object.getPrototypeOf(this ?? TodoV2);
return new ctor(title);
}
You shouldn't be using a static method for this. Instead, define a constructor for TodoV2:
class TodoV2 extends Todo {
constructor(title, description) {
super(title);
this.description = description ?? "";
}
static addTodo(title) { // Why no `description`?
return new this(title); // Or `new TodoV2(title)`
}
}
You might also look into the Symbol.species pattern if you want subclasses to create instances of superclasses.