How to add and remove a filter in a lookup field via javascript

formContext.getControl("lookupfilename").removePreSearch(FilterFunctioname); formContext.getControl("lookupfilename").addPreSearch(FilterFunctioname); function FilterFunctioname() { var filerFatchxml = "00000000-0000-0000-0000-000000000000"; formContext.getControl("lookupfilename").addCustomFilter(filerFatchxml); }