function createExtremum(comparator, exValue) {
	      return function(collection, iteratee, thisArg) {
	        if (thisArg && isIterateeCall(collection, iteratee, thisArg)) {
	          iteratee = undefined;
	        }
	        iteratee = getCallback(iteratee, thisArg, 3);
	        if (iteratee.length == 1) {
	          collection = isArray(collection) ? collection : toIterable(collection);
	          var result = arrayExtremum(collection, iteratee, comparator, exValue);
	          if (!(collection.length && result === exValue)) {
	            return result;
	          }
	        }
	        return baseExtremum(collection, iteratee, comparator, exValue);
	      };
	    }
Creates a `_.max` or `_.min` function.

@private
@param {Function} comparator The function used to compare values.
@param {*} exValue The initial extremum value.
@returns {Function} Returns the new extremum function.