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What are the criteria for judging bubbling operations?

PHPzOriginal: 2024-01-13 09:54:06439browse

How to determine whether an event can be bubbled?

Bubble operation means that when an event is triggered in the DOM tree, the event will automatically be passed upward to higher-level elements in the DOM tree. In JavaScript, we can determine whether an event can bubble by judging the bubbles attribute of the event.

The bubbles attribute in the event object is a Boolean value used to determine whether the current event can be bubbled. If bubbles is true, it means that the event can bubble; if bubbles is false, it means that the event will not bubble.

The following is a specific code example to demonstrate how to determine whether an event can be bubbled:

<!DOCTYPE html>
<html>
<head>
    <title>判断事件是否可以进行冒泡操作</title>
</head>
<body>
    <div id="outer">
        <div id="inner">
            <button id="btn">点击按钮</button>
        </div>
    </div>

    <script>
        document.getElementById("btn").addEventListener("click", function(event) {
            console.log("按钮被点击了");
            console.log("事件是否可以进行冒泡操作：" + event.bubbles);
        });

        document.getElementById("inner").addEventListener("click", function(event) {
            console.log("内层div被点击了");
            console.log("事件是否可以进行冒泡操作：" + event.bubbles);
        });

        document.getElementById("outer").addEventListener("click", function(event) {
            console.log("外层div被点击了");
            console.log("事件是否可以进行冒泡操作：" + event.bubbles);
        });
    </script>
</body>
</html>

In the above code, we created an outer div and an inner div div and a button. Click event listeners are added to the button, inner div, and outer div respectively. When they are clicked, corresponding information will be output, including whether the event can be bubbled.

By running the above code, we can see the following output in the browser's developer tools:

The button was clicked
Whether the event can be bubbled: true
The inner div was clicked
Whether the event can be bubbled: true
The outer div was clicked
Whether the event can be bubbled: true

From the output result, it is ok It can be seen that the click events of the button, inner div and outer div can all be bubbled because the values of their bubbles attributes are all true. So we can determine whether an event can bubble by judging the bubbles attribute of the event.

I hope that the above code examples can help everyone better understand how to determine whether an event can be bubbled.

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