Ember 3.16 Octane - Component not displaying in Application.hbs - ember.js

Question

I used ember generate to create a header component for a youtube video I am following. I have a few questions -
When I ran ember generate component header, the terminal responded with creating the header.hbs file in app>components, but then skips header.js in app/components. I manually created a header.js file in that directory and if I do an alert() in the js file it works.
I have the following code in my header.hbs file.
<h1>Hello There!</h1>
{{yield}}
In my application.hbs file :
<Header/>
{{outlet}}
thoughts, suggestions? Thank you for any help in advance!

Answer 1

Let me try to explain this a bit. Basically there are 4 kinds of components in ember.
without a .js file:
When you invoke a component ember will first look up the component class. When it does not find such a class the behavior depends on the optional feature template-only-glimmer-components. This is by default enabled for new octane apps.
If it is enabled ember will look up the component template based on some standard rules and use it, but there will be no backing class. That is pretty nice. This is also basically what you get in a octane app when you do ember g component my-component.
When template-only-glimmer-components is disabled then an implicit classic component class will automagically be created and used together with the correct template. You don't want this behavior. If you still have it you can migrate away from it by 1) creating a .js file for every component and then 2) enabling template-only-glimmer-components.
with a .js file
When a js file is found ember will get the default export of that module. Then it will look up the correct component manager. This actually depends on that export: setComponentManager should have been called on it. This is usually done in a base class as #ember/component or #glimmer/component.
But you can also write your own custom component manager.
Basically ember will then also look up the template based on that component. A public API for this is proposed in this RFC, but currently a private API is used for the so called template co-location where you place your .hbs file next to your .js file with the same name and just a different extension. This is the default in octant. Here a ember internal build-step in ember-cli basically adds your template to the .js file and uses that API. You can also see the result in a browser debugger. So when there is no default export then ember can not find your template.