element or forEach-capable list of elements for howLongMs, then
     removes it. If afterCallack is a function, it is called after the
     CSS class is removed from all elements. If called with 3
     arguments and the 3rd is a function, the 3rd is treated as a
     callback and the default time (addClassBriefly.defaultTimeMs) is
     used. If called with only 2 arguments, a time of
     addClassBriefly.defaultTimeMs is used.

     Passing a value of 0 for howLongMs causes the default value
     to be applied.

     Returns this object but the CSS removal is asynchronous.
  */
  dom.addClassBriefly = function f(e, className, howLongMs, afterCallback){
    if(arguments.length<4 && 'function'===typeof howLongMs){
      afterCallback = howLongMs;
      howLongMs = f.defaultTimeMs;
    }else if(arguments.length<3 || !+howLongMs){
      howLongMs = f.defaultTimeMs;
    }
    if(!e.forEach) e = [e];
    this.addClass(e, className);
    setTimeout(function(){
      dom.removeClass(e, className);
      if(afterCallback) afterCallback();
    }, howLongMs);
    return this;
  };