How to customize a callout marker in marker.js2?

[NQNghia]

Hi Ailon,

I watched your "Create a custom marker" tutorial and I'm trying to create a new callout marker with a background of a triangle. I copied all the code in TriangleMarker.js but inherited from CalloutMarker class. These are the errors that I get:

Could you give me some instructions for customizing a callout marker?

Thanks!