Pattern-Matching-Router aufgebaut auf WeakMap-Metadaten-Speicherung

const patternRegistry = new WeakMap();
 
class RoutePattern {
  constructor(matcherFn) {
    patternRegistry.set(this, matcherFn);
  }
 
  match(candidate) {
    const fn = patternRegistry.get(this);
    return fn ? fn(candidate) : false;
  }
}
 
const isUserEvent = new RoutePattern(val => typeof val === 'object' && val?.type === 'USER_ACTION');
const isSystemLog = new RoutePattern(val => typeof val === 'string' && val.startsWith('SYS_'));
 
function dispatch(event) {
  if (isUserEvent.match(event)) return 'Handling user action';
  if (isSystemLog.match(event)) return 'Handling system log';
  return 'Unhandled event format';
}
 
console.log(dispatch({ type: 'USER_ACTION', id: 42 }));