Feature request: testing whether a custom element extends a certain type

[jganetsk]

I would like to be able to call element.isSubClassOf('abstract-custom-element-type'). Looking at the tag name doesn't tell me this information. I'm not aware of how else to do this at teh moment.

[sorvell]

In general, you should use 'instanceof' to do this. There's a number of
ways to get the constructor for a custom element:

1. you can name it in your declaration and then it becomes a global:

2. you can get the constructor from an instance, e.g.

   XFoo =
   Object.getPrototypeOf(document.createElement('x-foo')).constructor;

Then if xbar descends from XFoo, you would do:

assert(xbar instanceof XFoo)

On Tue, Dec 17, 2013 at 3:04 PM, jganetsk notifications@github.com wrote:

I would like to be able to call
element.isSubClassOf('abstract-custom-element-type'). Looking at the tag
name doesn't tell me this information. I'm not aware of how else to do this
at teh moment.

—
Reply to this email directly or view it on GitHubhttps://github.com//issues/380
.

[jganetsk]

I could try to argue that this would be breaking the abstraction and peering into implementation details.

A better argument is a utility method would just come in handy.

[sorvell]

We can make use of this:

Polymer.getRegisteredPrototype('core-item').constructor