function addHandler()

in js/bootstrap.bundle.js [387:420]

• 31 lines of code
• 13 McCabe index (conditional complexity)

  function addHandler(element, originalTypeEvent, handler, delegationFunction, oneOff) {
    if (typeof originalTypeEvent !== 'string' || !element) {
      return;
    }
    let [isDelegated, callable, typeEvent] = normalizeParameters(originalTypeEvent, handler, delegationFunction);

    // 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 (originalTypeEvent in customEvents) {
      const wrapFunction = fn => {
        return function (event) {
          if (!event.relatedTarget || event.relatedTarget !== event.delegateTarget && !event.delegateTarget.contains(event.relatedTarget)) {
            return fn.call(this, event);
          }
        };
      };
      callable = wrapFunction(callable);
    }
    const events = getElementEvents(element);
    const handlers = events[typeEvent] || (events[typeEvent] = {});
    const previousFunction = findHandler(handlers, callable, isDelegated ? handler : null);
    if (previousFunction) {
      previousFunction.oneOff = previousFunction.oneOff && oneOff;
      return;
    }
    const uid = makeEventUid(callable, originalTypeEvent.replace(namespaceRegex, ''));
    const fn = isDelegated ? bootstrapDelegationHandler(element, handler, callable) : bootstrapHandler(element, callable);
    fn.delegationSelector = isDelegated ? handler : null;
    fn.callable = callable;
    fn.oneOff = oneOff;
    fn.uidEvent = uid;
    handlers[uid] = fn;
    element.addEventListener(typeEvent, fn, isDelegated);
  }