JavaScript drop-down menu function-JS Tutorial-php.cn

Home

Web Front-end

JS Tutorial

JavaScript drop-down menu function

高洛峰

Mar 01, 2017 pm 04:10 PM

This article mainly introduces the JavaScript drop-down menu example code, which is very good and has reference value. Friends who need it can refer to it

This article will share with you a piece of example code about the js implementation of the drop-down menu function, specifically The code is as follows:

<!doctype html> 
<html lang="en"> 
  <head> 
    <meta charset="UTF-8"> 
    <title>下拉菜单</title> 
    <style type="text/css"> 
      body, 
      ul, 
      li { 
        margin: 0; 
        padding: 0; 
        font-size: 13px; 
      } 
      ul, 
      li { 
        list-style: none; 
      } 
      #pselect { 
        width: 186px; 
        margin: 80px auto; 
        position: relative; 
        z-index: 10000; 
      } 
      #pselect cite { 
        width: 150px; 
        height: 24px; 
        line-height: 24px; 
        display: block; 
        color: #807a62; 
        cursor: pointer; 
        font-style: normal; 
        padding-left: 4px; 
        padding-right: 30px; 
        border: 1px solid #333333; 
        /*background: url(xjt.png) no-repeat right center;*/ 
      } 
      cite:before { 
        content: &#39;&#39;; 
        position: absolute; 
        right: 7px; 
        bottom: 7px; 
        width: 0; 
        height: 0; 
        border-width: 4px; 
        border-style: solid; 
        border-color: #888 transparent transparent transparent; 
        transition: all 0.2s; 
        -webkit-transition: all 0.2s; 
        -moz-transition: all 0.2s; 
        -o-transition: all 0.2s; 
        -ms-transition: all 0.2s; 
        transform-origin: 50% 25%; 
        -ms-transform-origin: 50% 25%; 
        -moz-transform-origin: 50% 25%; 
        -webkit-transform-origin: 50% 25%; 
        -o-transform-origin: 50% 25%; 
      } 
      .extended cite:before { 
        transform: rotate(180deg); 
        -webkit-transform: rotate(180deg); 
        -moz-transform: rotate(180deg); 
        -o-transform: rotate(180deg); 
        -ms-transform: rotate(180deg); 
      } 
      #pselect ul { 
        width: 184px; 
        border: 1px solid #333333; 
        background-color: #ffffff; 
        position: absolute; 
        z-index: 20000; 
        margin-top: -1px; 
        display: none; 
      } 
      #pselect ul li { 
        height: 24px; 
        line-height: 24px; 
      } 
      #pselect ul li a { 
        display: block; 
        height: 24px; 
        color: #333333; 
        text-decoration: none; 
        padding-left: 10px; 
        padding-right: 10px; 
      } 
      .animated { 
        animation-fill-mode: both; 
        -webkit-animation-fill-mode: both; 
        -moz-animation-fill-mode: both; 
        -o-animation-fill-mode: both; 
        -ms-animation-fill-mode: both; 
      } 
      .speed_fast { 
        animation-duration: .3s; 
        /*-webkit-animation-duration: 0.2s; 
        -moz-animation-duration: 0.2s; 
        -o-animation-duration: 0.2s; 
        -ms-animation-duration: 0.2s;*/ 
      } 
      .anim_extendDown { 
        animation-name: extendDown; 
        -webkit-animation-name: extendDown; 
        -moz-animation-name: extendDown; 
        -o-animation-name: extendDown; 
        -ms-animation-name: extendDown; 
      } 
      @keyframes extendDown { 
        0% { 
          border-bottom-color: transparent; 
          height: 0; 
        } 
        100% { 
          border-bottom-color: #333; 
          height: 120px; 
        } 
      } 
      @-webkit-keyframes extendDown { 
        0% { 
          border-bottom-color: transparent; 
          height: 0; 
        } 
        100% { 
          border-bottom-color: #333; 
          height: 120px; 
        } 
      } 
      @-moz-keyframes extendDown { 
        0% { 
          border-bottom-color: transparent; 
          height: 0; 
        } 
        100% { 
          border-bottom-color: #333; 
          height: 120px; 
        } 
      } 
      @-o-keyframes extendDown { 
        0% { 
          border-bottom-color: transparent; 
          height: 0; 
        } 
        100% { 
          border-bottom-color: #333; 
          height: 120px; 
        } 
      } 
      @-ms-keyframes extendDown { 
        0% { 
          border-bottom-color: transparent; 
          height: 0; 
        } 
        100% { 
          border-bottom-color: #333; 
          height: 120px; 
        } 
      } 
    </style> 
  </head> 
  <body> 
    <p id="pselect"> 
      <cite>请选择分类</cite> 
      <ul> 
        <li id="li"> 
          <a href="javascript:;" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" selectid="1">ASP开发</a> 
        </li> 
        <li> 
          <a href="javascript:;" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" selectid="2">.NET开发</a> 
        </li> 
        <li> 
          <a href="javascript:;" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" selectid="3">PHP开发</a> 
        </li> 
        <li> 
          <a href="javascript:;" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" selectid="4">Javascript开发</a> 
        </li> 
        <li> 
          <a href="javascript:;" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" selectid="5">Java特效</a> 
        </li> 
      </ul> 
    </p> 
    <script type="text/javascript"> 
      window.onload = function() { 
        var box = document.getElementById(&#39;pselect&#39;), 
          title = box.getElementsByTagName(&#39;cite&#39;)[0], 
          menu = box.getElementsByTagName(&#39;ul&#39;)[0], 
          as = box.getElementsByTagName(&#39;a&#39;), 
          index = -1; 
        //初始样式 
        function resetM() { 
          box.className = ""; 
          menu.className = ""; 
          menu.style.display = "none"; 
          index = -1; 
          resetA(); 
        } 
        //清空a选项样式 
        function resetA() { 
          for(var i = 0; i < as.length; i++) { 
            as[i].style.background = "#fff"; 
          } 
        } 
        // 点击三角时 
        title.onclick = function(event) { 
          //阻止事件冒泡 
          event = event || window.event; 
          event.stopPropagation ? event.stopPropagation() : event.cancelBubble = true; 
          if(box.className == "extended") { 
            resetM(); 
          } else { 
            box.className = "extended"; //给box加类名让三角旋转 
            menu.className = "animated speed_fast anim_extendDown"; //下拉菜单的下拉动画 
            menu.style.display = "block"; 
          } 
        } 
        document.onkeydown = function(event) { 
          event = event || window.event; 
          if(box.className == "extended") { 
            if(event.keyCode == 38) { //向上键 
              event.preventDefault ? event.preventDefault() : event.returnValue = false; 
              index--; 
              if(index == -1) { 
                index = as.length - 1; 
              } 
              resetA(); 
              as[index].style.background = "#ccc"; 
            } else if(event.keyCode == 40) { //向下键 
              event.preventDefault ? event.preventDefault() : event.returnValue = false; 
              index++; 
              if(index == as.length) { 
                index = 0; 
              } 
              resetA(); 
              as[index].style.background = "#ccc"; 
            } else if(event.keyCode == 13) { //回车键 
              event.preventDefault ? event.preventDefault() : event.returnValue = false; 
              title.innerHTML = as[index].innerHTML; 
              resetM(); 
            } 
          } 
        } 
        // 滑过滑过、离开、点击每个选项时 
        for(var i = 0; i < as.length; i++) { 
          as[i].onmouseover = function() { 
            resetA(); 
            this.style.background = "#ccc"; 
            index = this.getAttribute(&#39;selectid&#39;) - 1; 
          } 
          as[i].onclick = function() { 
            resetM(); 
            title.innerHTML = this.innerHTML; 
          } 
        } 
        // 点击页面空白处时 
        document.onclick = function() { 
          resetM(); 
        } 
      } 
    </script> 
  </body> 
</html>

1. To prevent event bubbling

2. For keyboard events, use index index

3. Add animation to elements and restore the original style by setting the class name or clearing the class name.

The above is the example code of the JavaScript drop-down menu function introduced by the editor. I hope it will be useful to you. Help, if you have any questions please leave me a message and the editor will reply to you in time. I would also like to thank you all for your support of the PHP Chinese website!

For more articles related to JavaScript drop-down menu functions, please pay attention to the PHP Chinese website!

Statement

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

JavaScript in Action: Real-World Examples and ProjectsApr 19, 2025 am 12:13 AM

JavaScript's application in the real world includes front-end and back-end development. 1) Display front-end applications by building a TODO list application, involving DOM operations and event processing. 2) Build RESTfulAPI through Node.js and Express to demonstrate back-end applications.

JavaScript and the Web: Core Functionality and Use CasesApr 18, 2025 am 12:19 AM

The main uses of JavaScript in web development include client interaction, form verification and asynchronous communication. 1) Dynamic content update and user interaction through DOM operations; 2) Client verification is carried out before the user submits data to improve the user experience; 3) Refreshless communication with the server is achieved through AJAX technology.

Understanding the JavaScript Engine: Implementation DetailsApr 17, 2025 am 12:05 AM

Understanding how JavaScript engine works internally is important to developers because it helps write more efficient code and understand performance bottlenecks and optimization strategies. 1) The engine's workflow includes three stages: parsing, compiling and execution; 2) During the execution process, the engine will perform dynamic optimization, such as inline cache and hidden classes; 3) Best practices include avoiding global variables, optimizing loops, using const and lets, and avoiding excessive use of closures.

Python vs. JavaScript: The Learning Curve and Ease of UseApr 16, 2025 am 12:12 AM

Python is more suitable for beginners, with a smooth learning curve and concise syntax; JavaScript is suitable for front-end development, with a steep learning curve and flexible syntax. 1. Python syntax is intuitive and suitable for data science and back-end development. 2. JavaScript is flexible and widely used in front-end and server-side programming.

Python vs. JavaScript: Community, Libraries, and ResourcesApr 15, 2025 am 12:16 AM

Python and JavaScript have their own advantages and disadvantages in terms of community, libraries and resources. 1) The Python community is friendly and suitable for beginners, but the front-end development resources are not as rich as JavaScript. 2) Python is powerful in data science and machine learning libraries, while JavaScript is better in front-end development libraries and frameworks. 3) Both have rich learning resources, but Python is suitable for starting with official documents, while JavaScript is better with MDNWebDocs. The choice should be based on project needs and personal interests.

From C/C to JavaScript: How It All WorksApr 14, 2025 am 12:05 AM

The shift from C/C to JavaScript requires adapting to dynamic typing, garbage collection and asynchronous programming. 1) C/C is a statically typed language that requires manual memory management, while JavaScript is dynamically typed and garbage collection is automatically processed. 2) C/C needs to be compiled into machine code, while JavaScript is an interpreted language. 3) JavaScript introduces concepts such as closures, prototype chains and Promise, which enhances flexibility and asynchronous programming capabilities.

JavaScript Engines: Comparing ImplementationsApr 13, 2025 am 12:05 AM

Different JavaScript engines have different effects when parsing and executing JavaScript code, because the implementation principles and optimization strategies of each engine differ. 1. Lexical analysis: convert source code into lexical unit. 2. Grammar analysis: Generate an abstract syntax tree. 3. Optimization and compilation: Generate machine code through the JIT compiler. 4. Execute: Run the machine code. V8 engine optimizes through instant compilation and hidden class, SpiderMonkey uses a type inference system, resulting in different performance performance on the same code.

Beyond the Browser: JavaScript in the Real WorldApr 12, 2025 am 12:06 AM

JavaScript's applications in the real world include server-side programming, mobile application development and Internet of Things control: 1. Server-side programming is realized through Node.js, suitable for high concurrent request processing. 2. Mobile application development is carried out through ReactNative and supports cross-platform deployment. 3. Used for IoT device control through Johnny-Five library, suitable for hardware interaction.

See all articles