Javascript事件侦听器没有按预期作出反应-有些事件没有触发

Question

我有下面这个简单的页面。

<style>
    #notifier {
        position: fixed;
        width: 320px;
        bottom: 0;
        left: 0;
        padding: 10px;
    }

    #notification-silo {
        width: 300px;
        height: 100%;
        position: relative;
    }

        #notification-silo .notification {
            position: absolute;
            bottom: 0;
            width: 300px;
            background-color: #fff;
            box-shadow: 2px 2px 8px 2px #666;
        }

        #notification-silo .header {
            background-color: #1266AB;
            color: #fff;
            padding: 5px;
        }

        #notification-silo .error .header {
            background-color: #1266AB;
        }

        #notification-silo .warning .header {
            background-color: #ff8f5f;
        }

        #notification-silo .header .title {
            width: 260px;
            display: inline-block;
        }

        #notification-silo .header .close-wrapper {
            display: inline-block;
        }

            #notification-silo .header .close-wrapper button {
                height: 25px;
                width: 25px;
                background-color: #2277bb;
                border: 0;
                color: #ff8f5f;
                border-radius: 50%;
            }

        #notification-silo .warning .header .close-wrapper button {
            background-color: #ffaa77;
            color: #2277bb;
        }

    #notifier .body {
        padding: 5px;
        border: 1px solid lightgray;
    }
</style>

<div id="notifier">
    <div id="notification-silo">
    </div>
</div>

<script>
    function show(html) {
        let notification, notificationArray, body, closeButton, existingNotificationHeights, sum, bottom, notification_template, siloElement, marginBetweenNotifications;

        siloElement = document.querySelector("#notification-silo");
        notification_template = `<div class="notification">
                                    <div class="header">
                                        <div class="title">Message</div>
                                        <div class="close-wrapper">
                                            <button>X</button>
                                        </div>
                                    </div>
                                    <div class="body"></div>
                                </div>`;
        marginBetweenNotifications = 10;

        // calculate position
        existingNotificationHeights = [...siloElement.children].map(notification => notification.offsetHeight);
        sum = existingNotificationHeights.length ? existingNotificationHeights.reduce((a, b) => a + b) : 0;
        bottom = sum + existingNotificationHeights.length * marginBetweenNotifications;

        // creat elements by update innerHTML
        siloElement.innerHTML += notification_template.trim();
        notificationArray = [...siloElement.querySelectorAll(".notification")];
        notification = notificationArray[notificationArray.length - 1];
        notification.style.bottom = bottom + "px";
        body = notification.querySelector(".body");
        body.innerHTML += html;

        // add event listener to close button
        closeButton = notification.querySelector(".close-wrapper button");
        closeButton.addEventListener("click", (ev) => {
            console.log("click is fired");
        });
    };
    
    show("System message 1");
    show("System message 2");
    show("System message 3");
    show("System message 4");
    show("System message 5");
</script>

它意味着通过show(msg)函数创建简单的通知消息。下面是有趣的部分--当创建少量消息并尝试将事件侦听器添加到它们的关闭按钮时，只有最后一个按钮获得一个侦听器并真正侦听单击事件。所有其他关闭按钮都不会对鼠标单击作出反应。你能帮我理解一下原因吗？

Answer 1

引用ProGu：

--我猜siloElement.innerHTML += notification_template.trim()删除了html内容，并重新分配了一次，因此删除了以前的事件.

Answer 2

只有你必须得到关闭按钮引用对象

    show("System message 1");
    show("System message 2");
    show("System message 3");
    show("System message 4");
    show("System message 5");

[].forEach.call(document.querySelectorAll("#notification-silo button.close-wrapper"),function(el){
      el.addEventListener("click",function(ev){
            var targetElement = ev.target || ev.srcElement;
            console.log(targetElement); //reference of button... 
      });
    });

或

<div class="close-wrapper">
     <button onClick="Close(this)">X</button>
</div>

或者完美如一种标准方式不使用静态html模板字符串使用动态纯JavaScript元素创建方法

例子：

let mainDiv = document.querySelector("#notification-silo");
let aTag = document.createElement('a');
aTag.innerHTML = "CLOSE TEXT....";
aTag.addEventListener("click", (ev) => {
        console.log("click is fired");
});
mainDiv.appendChild(aTag);