// All kinds of data
var websiteDataTypes = WKWebsiteDataStore.allWebsiteDataTypes();
// Date from
dateFrom = NSDate.dateWithTimeIntervalSince1970(0);
// Execute
WKWebsiteDataStore.defaultDataStore().removeDataOfTypesModifiedSinceCompletionHandler( websiteDataTypes, dateFrom, ()=> {
    console.log("DONE!!!!!!!!!!!!!!!!!!!!!!")
});