How we can add filter to the saved search and replace existing filter using script

 var filterOne = search.createFilter({
                    name: 'shipdate',
                    operator: search.operator.BEFORE,
                    values: tomorrowDate
                });
  log.debug("filterOne",filterOne);
 //replace the search filter createddate in the ui search with new filter
 var filer= filters.splice(2,1,filterOne)
 log.debug("filer",filer);
//Run the search result
var results = searcResult.run().getRange(0,1000);