With regards to IE specific code. Generally the approach I would take would: 1) Code normally and check compatibility of functions with the minimum version of

With regards to IE specific code. Generally the approach I would take would: 1) Code normally and check compatibility of functions with the minimum version of IE. I then either polyfill the browser (if I understand the polyfill, some polyfills are quite large). Where I don't understand what the polyfill is doing or it is quite large (more than 40 or 50 lines) I then implement a specific work around and try to put it that logic in a separate function e.g. for dataset on Elements I have a function that detects whether data set exists and then just uses setAttribute with some regex munging as 90% of the time I only need to read and write dataset values and I rarely care about dom mutations. 2) Regarding styling. My approach is to that I style everything up and then use specific overrides for things that browsers can't do. I also tend to avoid specific IE builds as you end up supporting almost two code bases. However I have years of intuition of what will and won't work in outdated browsers. However I appreciate that this isn't always possible or desirable depending on frameworks / libs used etc.