这两种JavaScript继承方式有什么区别

Question

Today I wasted hours in a weird bug while developing ember

I confidently ignored the Ember extend way

App.SomeModel = DS.Model.extend()

and somehow turned into my prefer way

class App.SomeModel extends DS.Model()

My second way just didn't work. So I want to know what's the difference between these two and why the second way didn't work in Ember(Cuz' both ways work in Backbone)

Answer 1

Look at EmberScript

http://emberscript.com/

The key difference is that the Class and extends compile directly to the Ember equivalents, rather than trying to make the Coffeescript ideas fit with Ember.

class SomeModel extends Ember.Object

becomes

var SomeModel;
var get$ = Ember.get;
var set$ = Ember.set;
SomeModel = Ember.Object.extend();

Answer 2

App.SomeModel = DS.Model.extend()

This calls Ember.js's own Object extend method, which adds observers, reopens a class and so on.

class App.SomeModel extends DS.Model()

Doesn't rely on a framework, In plain javascript, It's assigning "Somemodel" the properties of the "DS.Model()" object. It's not expected to work inside the framework for extending Ember.Object's