index.js
function _mergeOptions () {
  var options = {}
  for (var i = 0; i < arguments.length; ++i) {
    let obj = arguments[i]
    for (var attr in obj) { options[attr] = obj[attr] }
  }
  return options
}
function _mergeOptions () {
  var options = {}
  for (var i = 0; i < arguments.length; ++i) {
    let obj = arguments[i]
    for (var attr in obj) { options[attr] = obj[attr] }
  }
  return options
}
function _mergeOptions ( ) { var options = { } for ( var i = 0 ; i < arguments . length ; ++ i ) { let obj = arguments [ i ] for ( var attr in obj ) { options [ attr ] = obj [ attr ] } } return options }
merge all options objects front to back, i.e. later overriding earlier objects
merge all options objects front to back i . e . later overriding earlier objects