function invokeHandler(handler, vnode, event) {
    if (typeof handler === "function") {
        // call function handler
        handler.call(vnode, event, vnode);
    }
    else if (typeof handler === "object") {
        // call handler with arguments
        if (typeof handler[0] === "function") {
            // special case for single argument for performance
            if (handler.length === 2) {
                handler[0].call(vnode, handler[1], event, vnode);
            }
            else {
                var args = handler.slice(1);
                args.push(event);
                args.push(vnode);
                handler[0].apply(vnode, args);
            }
        }
        else {
            // call multiple handlers
            for (var i = 0; i < handler.length; i++) {
                invokeHandler(handler[i]);
            }
        }
    }
}
function handleEvent(event, vnode) {
    var name = event.type, on = vnode.data.on;
    // call event handler(s) if exists
    if (on && on[name]) {
        invokeHandler(on[name], vnode, event);
    }
}
function createListener() {
    return function handler(event) {
        handleEvent(event, handler.vnode);
    };
}
function updateEventListeners(oldVnode, vnode) {
    var oldOn = oldVnode.data.on, oldListener = oldVnode.listener, oldElm = oldVnode.elm, on = vnode && vnode.data.on, elm = (vnode && vnode.elm), name;
    // optimization for reused immutable handlers
    if (oldOn === on) {
        return;
    }
    // remove existing listeners which no longer used
    if (oldOn && oldListener) {
        // if element changed or deleted we remove all existing listeners unconditionally
        if (!on) {
            for (name in oldOn) {
                // remove listener if element was changed or existing listeners removed
                oldElm.removeEventListener(name, oldListener, false);
            }
        }
        else {
            for (name in oldOn) {
                // remove listener if existing listener removed
                if (!on[name]) {
                    oldElm.removeEventListener(name, oldListener, false);
                }
            }
        }
    }
    // add new listeners which has not already attached
    if (on) {
        // reuse existing listener or create new
        var listener = vnode.listener = oldVnode.listener || createListener();
        // update vnode for listener
        listener.vnode = vnode;
        // if element changed or added we add all needed listeners unconditionally
        if (!oldOn) {
            for (name in on) {
                // add listener if element was changed or new listeners added
                elm.addEventListener(name, listener, false);
            }
        }
        else {
            for (name in on) {
                // add listener if new listener added
                if (!oldOn[name]) {
                    elm.addEventListener(name, listener, false);
                }
            }
        }
    }
}
export var eventListenersModule = {
    create: updateEventListeners,
    update: updateEventListeners,
    destroy: updateEventListeners
};
export default eventListenersModule;
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