How to create a drop-down menu in JavaScript-JS Tutorial-php.cn

How to create a drop-down menu in JavaScript

藏色散人

Release： 2021-07-03 10:01:28

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How to make a drop-down menu with JavaScript: 1. Use the value attribute to get the options of the drop-down menu; 2. Determine the status of the div based on the options; 3. Use the style.display style to hide or display the div.

How to create a drop-down menu in JavaScript

The operating environment of this article: windows7 system, javascript version 1.8.5, Dell G3 computer.

How to create a drop-down menu with JavaScript?

js drop-down menu production

1. Use js to hide and display divs through drop-down menus

Idea: Use the value attribute Get the options of the drop-down menu → determine the status of the div based on the options → use the style.display style to hide or show the div. An example demonstration is as follows:

Code

<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>W3Cschool(w3cschool.cn)</title>
</head>
<body>
  <select id="test_select">
    <option value="1">显示</option>
    <option value="2">隐藏</option>
  </select>
  <div id="test">我是一个div么呀我是一个div</div>
  <script>
    window.onload = function () {
      var obj_select = document.getElementById("test_select");
      var obj_div = document.getElementById("test");
      obj_select.onchange = function () {
        obj_div.style.display = this.value == 1 ? "block" : "none";
      }
    }
  </script>
</body>
</html>

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Effect demonstration

How to create a drop-down menu in JavaScript

## 2. How to use js to display a drop-down menu when the mouse slides over it

The general idea is as follows: first set the width and height of the menu box and add position: relative; then set the same width and height for the content inside; then add absolute positioning of width to the drop-down secondary menu inside.

<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>W3Cschool(w3cschool.cn)</title>
  <style>
    * {
      margin: 0;
      padding: 0;
    }
    li {
      list-style-type: none;
    }
    a {
      text-decoration: none;
      font-size: 14px;
    }
    .nav {
      margin: 100px;
    }
    .nav>li {
      position: relative;
      float: left;
      width: 80px;
      height: 41px;
      text-align: center;
    }
    .nav li a {
      display: block;
      width: 100%;
      height: 100%;
      line-height: 41px;
      color: #333;
    }
    .nav>li>a:hover {
      background-color: #eee;
    }
    .nav ul {
      display: none;
      position: absolute;
      top: 41px;
      left: 0;
      width: 100%;
      border-left: 1px solid #FECC5B;
      border-right: 1px solid #FECC5B;
    }
    .nav ul li {
      border-bottom: 1px solid #FECC5B;
    }
    .nav ul li a:hover {
      background-color: #FFF5DA;
    }
  </style>
</head>
<body>
  <ul>
    <li>
      <a href="javascript:;">下拉</a>
      <ul>
        <li><a href="javascript:;">下拉1</a></li>
        <li><a href="javascript:;">下拉2</a></li>
        <li><a href="javascript:;">下拉3</a></li>
        <li><a href="javascript:;">下拉4</a></li>
      </ul>
    </li>
  </ul>
  <script>
    var lis = document.querySelector(&#39;.nav&#39;).children;
    for (var i = 0; i < lis.length; i++) {
      lis[i].onmouseover = function () {
        this.children[i].style.display = &#39;block&#39;;
      }
      lis[i].onmouseout = function () {
        this.children[i].style.display = &#39;none&#39;;
      }
    }
  </script>
</body>
</html>

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