Get the difference in styles between two HTML nodes

delta.js

function styleDelta(a, b) {
  var aStyles = window.getComputedStyle(a)
    , bStyles = window.getComputedStyle(b)
    , delta = {}
  
  Object.keys(aStyles).forEach(function(key) { 
    var aVal = aStyles[key]
      , bVal = bStyles[key]

    if (aVal != bVal) {
      delta[key] = [aVal, bVal]
    }
  })

  return delta
}