Code example for implementing multi-level menu bar using JS-JS Tutorial-php.cn

Home

Web Front-end

JS Tutorial

Code example for implementing multi-level menu bar using JS

Y2J

May 24, 2017 am 11:32 AM

Recently, there is a project to implement N-level menus. First, start with the layout, that is, determine whether there are lower-level menus, and the specific implementation code. You can refer to this article

Requirements Analysis

A simple analysis, to implement an N-level menu, first start with the layout, that is, determine whether there is a lower-level menu

1. If there is no lower-level menu, arrange it directly

2. There is a lower-level menu, which is divided into the lower-level menu placement position and a symbol similar to '>' displayed on the upper-level menu. The effect is as shown in the figure:

##Picture ：1

## Initial implementation1. Whether the implementation exists >

Note: Any concerns below xxx=== yyy ? xxx : xxx all use the ternary

expression

to express ideas. HTML structure is as follows:

Figure: 2

•To achieve the effect of Figure 1, we only need to determine the content in the li tag children.length===2 ? 'span exists' : 'span remove'

2. The location where the lower-level menu appears

HTML structure is as follows:

•To achieve this requirement, you also need to determine children.length===2? 'The upper-level menu is relatively positioned, top is 0, left is the upper-level offsetWidth, and the lower-level menu is absolutely positioned': 'No processing'

The specific code is to realize The effect diagram is as follows:

The code is as follows:

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style type="text/css">
    * {
      margin: 0;
      padding: 0;
    }
    #box {
      margin: 200px 0 0 50px;
      text-align: center;
      color: #ccc;
    }
    ul {
      list-style: none;
      float: left;
    }
    li {
      width: 150px;
      height: 40px;
      line-height: 40px;
      background-color: #124520;
      border: 1px solid #eee;
      position: relative;
    }
    li span {
      position: absolute;
      top: 0;
      right: 10px;
    }
    li:hover {
      background-color: #666;
      transition: background-color .5s;
    }
    ul {
      display: none;
    }
    ul.first {
      display: block;
    }
    .relative {
      position:relative;
      top: 0;
      left: 0;
    }
    .absolute {
      position: absolute;
      left: 0;
      top: 0;
    }
    .show {
      display: block;
    }
    .hide {
      display: none;
    }
  </style>
</head>
<body>
  <p id="box">
    <ul class="first">
      <li>一级菜单
        <span>></span>
      </li>
      <li>一级菜单
        <span>></span>
        <ul>
          <li>二级菜单
            <span>></span>
            <ul>
              <li>三级菜单
                <span>></span>
              </li>
              <li>三级菜单
                <span>></span>
              </li>
              <li>三级菜单
                <span>></span>
              </li>
              <li>三级菜单
                <span>></span>
              </li>
            </ul>
          </li>
          <li>二级菜单
            <span>></span>
            <ul>
              <li>三级菜单
                <span>></span>
              </li>
              <li>三级菜单
                <span>></span>
              </li>
              <li>三级菜单
                <span>></span>
              </li>
              <li>三级菜单
                <span>></span>
              </li>
            </ul>
          </li>
          <li>二级菜单
            <span>></span>
          </li>
          <li>二级菜单
            <span>></span>
            <ul>
              <li>三级菜单
                <span>></span>
              </li>
              <li>三级菜单
                <span>></span>
              </li>
              <li>三级菜单
                <span>></span>
              </li>
              <li>三级菜单
                <span>></span>
              </li>
            </ul>
          </li>
        </ul>
      </li>
      <li>一级菜单
        <span>></span>
        <ul>
          <li>二级菜单
            <span>></span>
          </li>
          <li>二级菜单
            <span>></span>
            <ul>
              <li>三级菜单
                <span>></span>
              </li>
              <li>三级菜单
                <span>></span>
              </li>
              <li>三级菜单
                <span>></span>
              </li>
            </ul>
          </li>
          <li>二级菜单
            <span>></span>
            <ul>
              <li>三级菜单
                <span>></span>
              </li>
              <li>三级菜单
                <span>></span>
              </li>
              <li>三级菜单
                <span>></span>
              </li>
              <li>三级菜单
                <span>></span>
              </li>
            </ul>
          </li>
          <li>二级菜单
            <span>></span>
            <ul>
              <li>三级菜单
                <span>></span>
              </li>
              <li>三级菜单
                <span>></span>
              </li>
              <li>三级菜单
                <span>></span>
              </li>
              <li>三级菜单
                <span>></span>
              </li>
            </ul>
          </li>
        </ul>
      </li>
      <li>一级菜单
        <span>></span>
      </li>
    </ul>
  </p>
</body>
<script type="text/javascript">
let uls = document.querySelectorAll("ul"); //获取所有的ul
let lis = document.querySelectorAll("li"); //获取所有的li
let liWidth = document.querySelector("#box ul").offsetWidth-2 //li的宽度 -2是为了好看
/* 布局start */
/*
 * 
 * 通过下面布局中代码实现每个 li.children.length 要么为0 要么为2
 * 0 无下级菜单
 * 2 有下级菜单
 * 
 */
for (let i = uls.length - 1; i >= 0; i--) {
  if(uls[i].parentNode.nodeName === "LI") {
    uls[i].parentNode.classList.add("relative"); //相对定位
    uls[i].classList.add("absolute"); // 绝对定位
    uls[i].style.left = liWidth + "px"; 
  }
}
for (var i = 0; i < lis.length; i++) {
  if( lis[i].children.length === 1) { //没有下一级菜单直接删除
    lis[i].children[0].outerHTML = "";
  };
}
/* 布局end */
for (let i = 0; i < lis.length; i++) { // 控制每一个li
  lis[i].onmouseover = function() {
    if( lis[i].children.length === 2) {
      this.children[1].classList.remove("hide");
      this.children[1].classList.add("show");
    } 
  }
  lis[i].onmouseout = function() {
    if( lis[i].children.length === 2) {
      this.children[1].classList.remove("show");
      this.children[1].classList.add("hide");
    }
  }
}
</script>
</html>

Copy after login

【Related recommendations】

Javascript Free Video Tutorial

JS Code examples for making QQ chat message display and comment submission functions

Single line of JS to implement mobile money format inspection

JavaScript form Verify implementation code_javascript skills

Detailed examples of commonly used middleware body-parser in Nodejs

The above is the detailed content of Code example for implementing multi-level menu bar using JS. For more information, please follow other related articles on the PHP Chinese website!

Statement of this Website

The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress images for free

Clothoff.io

AI clothes remover

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)

2 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

Repo: How To Revive Teammates

4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

Hello Kitty Island Adventure: How To Get Giant Seeds

3 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

How Long Does It Take To Beat Split Fiction?

3 weeks ago By DDD

R.E.P.O. Save File Location: Where Is It & How to Protect It?

3 weeks ago By DDD

Hot Tools

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

God-level code editing software (SublimeText3)

Hot Topics

Where is the login entrance for gmail email?

7316

Java Tutorial

1625

CakePHP Tutorial

1349

Laravel Tutorial

1261

PHP Tutorial

1208

Related knowledge

How to use JS and Baidu Maps to implement map pan function Nov 21, 2023 am 10:00 AM

How to use JS and Baidu Map to implement map pan function Baidu Map is a widely used map service platform, which is often used in web development to display geographical information, positioning and other functions. This article will introduce how to use JS and Baidu Map API to implement the map pan function, and provide specific code examples. 1. Preparation Before using Baidu Map API, you first need to apply for a developer account on Baidu Map Open Platform (http://lbsyun.baidu.com/) and create an application. Creation completed

Essential tools for stock analysis: Learn the steps to draw candle charts with PHP and JS Dec 17, 2023 pm 06:55 PM

Essential tools for stock analysis: Learn the steps to draw candle charts in PHP and JS. Specific code examples are required. With the rapid development of the Internet and technology, stock trading has become one of the important ways for many investors. Stock analysis is an important part of investor decision-making, and candle charts are widely used in technical analysis. Learning how to draw candle charts using PHP and JS will provide investors with more intuitive information to help them make better decisions. A candlestick chart is a technical chart that displays stock prices in the form of candlesticks. It shows the stock price

Recommended: Excellent JS open source face detection and recognition project Apr 03, 2024 am 11:55 AM

Face detection and recognition technology is already a relatively mature and widely used technology. Currently, the most widely used Internet application language is JS. Implementing face detection and recognition on the Web front-end has advantages and disadvantages compared to back-end face recognition. Advantages include reducing network interaction and real-time recognition, which greatly shortens user waiting time and improves user experience; disadvantages include: being limited by model size, the accuracy is also limited. How to use js to implement face detection on the web? In order to implement face recognition on the Web, you need to be familiar with related programming languages and technologies, such as JavaScript, HTML, CSS, WebRTC, etc. At the same time, you also need to master relevant computer vision and artificial intelligence technologies. It is worth noting that due to the design of the Web side

PHP and JS Development Tips: Master the Method of Drawing Stock Candle Charts Dec 18, 2023 pm 03:39 PM

With the rapid development of Internet finance, stock investment has become the choice of more and more people. In stock trading, candle charts are a commonly used technical analysis method. It can show the changing trend of stock prices and help investors make more accurate decisions. This article will introduce the development skills of PHP and JS, lead readers to understand how to draw stock candle charts, and provide specific code examples. 1. Understanding Stock Candle Charts Before introducing how to draw stock candle charts, we first need to understand what a candle chart is. Candlestick charts were developed by the Japanese

How to create a stock candlestick chart using PHP and JS Dec 17, 2023 am 08:08 AM

How to use PHP and JS to create a stock candle chart. A stock candle chart is a common technical analysis graphic in the stock market. It helps investors understand stocks more intuitively by drawing data such as the opening price, closing price, highest price and lowest price of the stock. price fluctuations. This article will teach you how to create stock candle charts using PHP and JS, with specific code examples. 1. Preparation Before starting, we need to prepare the following environment: 1. A server running PHP 2. A browser that supports HTML5 and Canvas 3

How to use JS and Baidu Maps to implement map polygon drawing function Nov 21, 2023 am 10:53 AM

How to use JS and Baidu Maps to implement map polygon drawing function. In modern web development, map applications have become one of the common functions. Drawing polygons on the map can help us mark specific areas for users to view and analyze. This article will introduce how to use JS and Baidu Map API to implement map polygon drawing function, and provide specific code examples. First, we need to introduce Baidu Map API. You can use the following code to import the JavaScript of Baidu Map API in an HTML file

How to use JS and Baidu Map to implement map click event processing function Nov 21, 2023 am 11:11 AM

Overview of how to use JS and Baidu Maps to implement map click event processing: In web development, it is often necessary to use map functions to display geographical location and geographical information. Click event processing on the map is a commonly used and important part of the map function. This article will introduce how to use JS and Baidu Map API to implement the click event processing function of the map, and give specific code examples. Steps: Import the API file of Baidu Map. First, import the file of Baidu Map API in the HTML file. This can be achieved through the following code:

How to use JS and Baidu Maps to implement map heat map function Nov 21, 2023 am 09:33 AM

How to use JS and Baidu Maps to implement the map heat map function Introduction: With the rapid development of the Internet and mobile devices, maps have become a common application scenario. As a visual display method, heat maps can help us understand the distribution of data more intuitively. This article will introduce how to use JS and Baidu Map API to implement the map heat map function, and provide specific code examples. Preparation work: Before starting, you need to prepare the following items: a Baidu developer account, create an application, and obtain the corresponding AP

See all articles