function addHandler()

in src/site/assets/js/bootstrap.bundle.js [429:475]
39 lines of code
15 McCabe index (conditional complexity)

  function addHandler(element, originalTypeEvent, handler, delegationFn, oneOff) {
    if (typeof originalTypeEvent !== 'string' || !element) {
      return;
    }

    if (!handler) {
      handler = delegationFn;
      delegationFn = null;
    } // in case of mouseenter or mouseleave wrap the handler within a function that checks for its DOM position
    // this prevents the handler from being dispatched the same way as mouseover or mouseout does


    if (customEventsRegex.test(originalTypeEvent)) {
      const wrapFn = fn => {
        return function (event) {
          if (!event.relatedTarget || event.relatedTarget !== event.delegateTarget && !event.delegateTarget.contains(event.relatedTarget)) {
            return fn.call(this, event);
          }
        };
      };

      if (delegationFn) {
        delegationFn = wrapFn(delegationFn);
      } else {
        handler = wrapFn(handler);
      }
    }

    const [delegation, originalHandler, typeEvent] = normalizeParams(originalTypeEvent, handler, delegationFn);
    const events = getEvent(element);
    const handlers = events[typeEvent] || (events[typeEvent] = {});
    const previousFn = findHandler(handlers, originalHandler, delegation ? handler : null);

    if (previousFn) {
      previousFn.oneOff = previousFn.oneOff && oneOff;
      return;
    }

    const uid = getUidEvent(originalHandler, originalTypeEvent.replace(namespaceRegex, ''));
    const fn = delegation ? bootstrapDelegationHandler(element, handler, delegationFn) : bootstrapHandler(element, handler);
    fn.delegationSelector = delegation ? handler : null;
    fn.originalHandler = originalHandler;
    fn.oneOff = oneOff;
    fn.uidEvent = uid;
    handlers[uid] = fn;
    element.addEventListener(typeEvent, fn, delegation);
  }