- Are you assuming full ES5 support when building libraries?
- Are you assuming partial ES6 support when building libraries?
- Are you pushing shim responsibility to the user?
- Are you ignoring browsers that are 1% or lower in market share?
- When should a library stop hand-holding older systems?
What's your opinion? When should a library shed off legacy browser code?
(legacy = IE10 and below, browsers older than the previous version)