How to implement left secondary navigation in javascript

With the rapid development of Web front-end technology, JavaScript has been widely used in various Web applications. In web design, the navigation bar is one of the most important elements. It is the main entrance for users to enter the website and is also an important part of the overall structure of the website. This article will introduce how to implement the JavaScript left secondary navigation bar.

The navigation bar is one of the most basic components of the website and is mainly used to navigate various pages in the entire website. However, the navigation bar often appears to be too long on the page. In this case, we usually use a secondary navigation bar to solve this problem. This article will introduce how to use JavaScript to implement a left secondary navigation bar, and briefly explain its implementation principle.

Before implementing the left secondary navigation bar, you need to first master several necessary concepts and technologies. These include HTML, CSS, and JavaScript.

1. HTML

HTML is a markup language used to describe web content. HTML tags are used to define and describe various elements on the page, including text and images. , links, etc. When implementing the left secondary navigation bar, you need to use HTML to define the structure of the navigation bar.

2. CSS

CSS is a markup language used to describe web page styles. CSS style sheets are used to define and describe the appearance and layout of various elements on the page. . When implementing the left secondary navigation bar, you need to use CSS to define the style and layout of the navigation bar.

3. JavaScript

JavaScript is a programming language used to develop web applications. Its syntax and semantics are similar to the C language. When implementing the left secondary navigation bar, JavaScript needs to be used to realize the interactive and dynamic effects of the navigation bar.

Now let’s start our implementation steps.

Step 1: HTML structure

First, we need to use HTML to define the structure of the navigation bar, including the main navigation bar and secondary navigation bar. The main navigation bar is the entrance to the entire website, while the secondary navigation bar is a submenu of the main navigation bar, used to display some content of the main navigation bar. The following is a simple HTML structure used to implement the left secondary navigation bar:

<div class="sidebar">
   <ul class="main-nav">
      <li><a href="#">Home</a></li>
      <li><a href="#">Products</a>
         <ul class="sub-nav">
            <li><a href="#">Product 1</a></li>
            <li><a href="#">Product 2</a></li>
            <li><a href="#">Product 3</a></li>
         </ul>
      </li>
      <li><a href="#">Services</a>
         <ul class="sub-nav">
            <li><a href="#">Service 1</a></li>
            <li><a href="#">Service 2</a></li>
            <li><a href="#">Service 3</a></li>
         </ul>
      </li>
      <li><a href="#">About Us</a></li>
      <li><a href="#">Contact Us</a></li>
   </ul>
</div>

In the above code, we use a div and a ul element to represent the navigation bar. Among them, the ul element is divided into two parts: the main navigation bar and the secondary navigation bar. The main navigation bar is represented by li and a tags, while the secondary navigation bar is represented by nested ul, li and a tags.

Step 2: CSS Style

Next, we need to use CSS styles to define the style and layout of the navigation bar. The style sheet is located in the