直入正题：

<p id="box" class="blue">
    box
    <p id="child-box" class="blue">
        child box
    </p>
</p>



<button id="btn">触发事件</button>



<

script>

    var evt = new Event('customEvent');

    var eventBox = document.getElementById('box');
    var eventChildBox = document.getElementById('child-box');

    function customEventCallback(e) {
        console.log('run ' + e.target.getAttribute('id'));
    }

    eventChildBox.addEventListener('customEvent', customEventCallback, false);
    eventBox.addEventListener('customEvent', customEventCallback, false);


    //测试代码
    var btn = document.getElementById('btn');

    btn.onclick = function(e) {
        eventChildBox.dispatchEvent(evt);
    };

为什么单击按钮只会触发一次，且输出是

run child-box

哪位大师能指点一下？