(clss → string | object | array, el → dom)
- add and remove class of element
function (clss, el) {
  if (isString(clss)) classList(el).add(clss)
  if (isObject(clss)) {
    var classArr = el.className.split(' ')
    var key
    for (key in clss) {
      if (classArr.indexOf(key) && clss[key] === false) classList(el).remove(key)
      if (clss.hasOwnProperty(key) && clss[key] === true) classList(el).add(key)
    }
  }
  if (isArray(clss)) {
    var i
    for (i = 0;i < clss.length; i++) {
      classList(el).add(clss[i])
    }
  }
}