lib/util/setadd.js
function setadd(set, element) {
  if (set.has(element)) return false;
  set.add(element);
  return true;
}
function setadd(set, element) {
  if (set.has(element)) return false;
  set.add(element);
  return true;
}
function setadd ( set , element ) { if ( set . has ( element ) ) return false ; set . add ( element ) ; return true ; }
Adds an element to a set and returns true if the set has changed.

@param {Set} set - The set to add to.
@param {Object} element - The element to add to the set.
@returns {Boolean} Whether <code>set</code> has changed.
Adds an element to a set and returns true if the set has changed .