JavaScript bubbling event practice: Learn how to apply bubbling events to solve practical problems through examples

JavaScript bubbling event practice: learn how to apply bubbling events to solve practical problems through examples

Introduction:
In web development, we often encounter needs Event handling on the page. JavaScript provides a variety of event handling mechanisms, among which bubbling events are the most commonly used and powerful one. Through bubbling events, we can more easily handle complex interactive logic on the page. In this article, I will use specific examples to introduce in detail how to apply bubbling events to solve practical problems, and provide corresponding JavaScript code examples.

1. What is a bubbling event?
A bubbling event means that when an element triggers a specific event, the event will first be processed by the element itself and then passed to the upper element. until it is passed to the top-most element. This event delivery method is like water bubbles rising up, so it is called a bubbling event. Bubbling events can be applied to all elements, including text boxes, buttons, drop-down lists, etc.

2. Application scenarios of bubbling events
The application scenarios of bubbling events are very wide. Here are a few common examples to illustrate the practical application of bubbling events:

1. Dynamic binding event handling function: When we create a large number of elements in the page, if each element needs to be bound to the same event handling function, then using bubbling events can simplify the process. We only need to bind the event handler function to the parent element and then pass it to the child elements through bubbling events.
2. Click event of list item: When we need to process a list and click on the list item, we need to trigger the corresponding operation. This can be achieved through bubbling events. We only need to bind the click event to the parent element of the list, then obtain the specific clicked list item through the event object, and perform corresponding operations.
3. Form validation: In form validation, the input box's lost focus event is very important. When the input box loses focus, we need to validate the input content. By bubbling events, we can bind the focus loss event to the parent element of the form instead of binding the same event handler to each input box.

3. Basic characteristics of bubbling events
When using bubbling events, we need to understand their basic characteristics in order to better apply them to actual problems.

1. Event propagation direction: Bubble events are propagated from bottom to top, starting from the element that triggered the event, passed from bottom to top to the parent element, and finally to the top-level element.
2. Event firing order: If an element is bound to multiple bubbling events at the same time, their firing order is determined based on their position in the HTML document, with elements closer to the top firing first.
3. Prevent bubbling of events: If we want to prevent the bubbling event of an element from being passed to the upper element, we can use the stopPropagation() method of the event object to achieve this.

4. Example analysis: Achieving Tab switching effect through bubbling events
In order to better understand and master the application of bubbling events, let’s look at a specific example: through bubbling events Implement Tab switching effect.

In a page, there are multiple Tab labels. When you click on different Tab labels, different content will be displayed. First, we bind a click event to each Tab label and trigger the corresponding operation when clicked. However, if each Tab label is bound to the same event handling function, it will cause code duplication and be inconvenient to maintain. At this time, we can use bubbling events to bind the click event to the parent element, and obtain the specific clicked Tab tag based on the event object, thereby achieving the Tab switching effect.

The following is a code example:

window.onload = function() {
  var tabs = document.getElementById('tabs');
  var content = document.getElementById('content');

  tabs.addEventListener('click', function(event) {
    var target = event.target;
    if (target.tagName.toLowerCase() === 'li') {
      var active = tabs.querySelector('.active');
      var index = Array.prototype.indexOf.call(tabs.children, target);

      if (active) {
        active.classList.remove('active');
      }
      target.classList.add('active');

      var activeContent = content.querySelector('.active');
      if (activeContent) {
        activeContent.classList.remove('active');
      }
      content.children[index].classList.add('active');
    }
  });
};

In this example, we first bind the click event to the tabs element through event delegation, and then obtain the specific information through the target attribute of the event object. Click on the label. Then, we perform corresponding operations according to the clicked label to achieve the Tab switching effect.

Summary:
Through the above examples, we can find that bubbling events are a very powerful and practical event processing mechanism. Through reasonable application, we can simplify the code, improve efficiency, and better handle complex interaction logic. I hope that through the introduction and examples of this article, readers will have a deeper understanding of bubbling events and be able to apply them to actual development.

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