Determine desired browser support

What browsers do I want to support?

Object.observe is obv. optimal, but that basically means pre-releases of modern browsers. If I do that, though, I can rely on Array.each and other nice things.

I'm also using classList in interactiveUtil, which is IE10+.

Questions to ask myself: What are the use cases for this library? What are the limiting factors for make it more compatible? What would it look like in all of these different scenarios (size of the library, etc.)?

Start by reviewing the library's use cases and the browser APIs mentioned in the issue, especially Object.observe, Array.each, and classList in interactiveUtil. Compare the compatibility and library-size implications of the possible support ranges. Done means a decided browser-support policy and a documented rationale for the chosen compatibility trade-offs.

Written by the indexing model from the issue text.