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Small functions implemented with javascript

王林Original: 2023-05-09 17:47:07542browse

JavaScript is a high-level, dynamic, object-oriented programming language that can be combined with HTML and CSS to create powerful web applications. This article will introduce some small functions implemented using JavaScript to help you better understand the application of JavaScript.

Click the button to change the text

This is a very basic JavaScript application, and the implementation method is also very simple. You can create a button and add an onclick event handler to it. When the button is clicked, the JavaScript code will modify the associated text. For example:

<!DOCTYPE html>
<html>
<head>
  <title>点击按钮改变文本</title>
</head>
<body>
  <h1 id="header">欢迎来到我的网站</h1>
  <button onclick="changeText()">点击修改标题</button>

  <script>
    function changeText() {
      var header = document.getElementById("header");
      header.innerHTML = "欢迎访问我的个人博客";
    }
  </script>
</body>
</html>

Timer

JavaScript can also be used to create timers, which is very useful for some applications that require timing. You can use the setInterval() function to implement a timer. For example:

<!DOCTYPE html>
<html>
<head>
  <title>计时器</title>
</head>
<body>
  <h1>倒计时：</h1>
  <p id="timer"></p>

  <script>
    var count = 60;
    var timer = document.getElementById("timer");

    var interval = setInterval(function(){
      count--;
      timer.innerHTML = count + "秒";
      if (count === 0) {
        clearInterval(interval);
        timer.innerHTML = "时间到！";
      }
    }, 1000);
  </script>
</body>
</html>

Confirmation dialog box

Sometimes it is necessary to ask the user to confirm whether to perform an operation. JavaScript can be used to create confirmation dialog boxes that allow users to make choices. For example:

<!DOCTYPE html>
<html>
<head>
  <title>确认对话框</title>
</head>
<body>
  <button onclick="showConfirm()">点击删除</button>

  <script>
    function showConfirm() {
      var choice = confirm("您确定要删除这个文件吗？");
      if (choice) {
        alert("文件已成功删除！");
      } else {
        alert("删除操作已取消。");
      }
    }
  </script>
</body>
</html>

Form validation

Form validation is a very common JavaScript application. You can check the form to ensure that the content entered by the user meets the requirements. For example:

<!DOCTYPE html>
<html>
<head>
  <title>表单验证</title>
  <script>
    function validateForm() {
      var name = document.forms["myForm"]["name"].value;
      var phone = document.forms["myForm"]["phone"].value;

      if (name === "") {
        alert("请输入您的姓名。");
        return false;
      }

      if (phone === "") {
        alert("请输入您的电话号码。");
        return false;
      }

      // 电话号码必须是数字
      if (isNaN(phone)) {
        alert("电话号码必须是数字。");
        return false;
      }
    }
  </script>
</head>
<body>
  <h1>请填写以下表单：</h1>
  <form name="myForm" onsubmit="return validateForm()">
    姓名：<input type="text" name="name"><br>
    电话：<input type="text" name="phone"><br>
    <input type="submit" value="提交">
  </form>
</body>
</html>

Picture Carousel

JavaScript can also be used to create dynamic picture carousels. You can use JavaScript to set a div element containing multiple images, and then use the setInterval() function to switch images. For example:

<!DOCTYPE html>
<html>
<head>
  <title>图片轮播</title>
  <style>
    #slideshow {
      width: 400px;
      height: 300px;
      position: relative;
      overflow: hidden;
    }
    #slideshow img {
      width: 400px;
      height: 300px;
      position: absolute;
      top: 0;
      left: 0;
    }
  </style>
</head>
<body>
  <div id="slideshow">
    <img src="img1.jpg" />
    <img src="img2.jpg" />
    <img src="img3.jpg" />
  </div>

  <script>
    var currentImg = 0;
    var imgList = document.querySelectorAll("#slideshow img");

    setInterval(function() {
      imgList[currentImg].style.opacity = 0;
      currentImg = (currentImg + 1) % imgList.length;
      imgList[currentImg].style.opacity = 1;
    }, 2000);
  </script>
</body>
</html>

Summary

JavaScript is a very powerful programming language that can be used to create a variety of web applications. This article introduces some JavaScript usage, including changing text on button clicks, timers, confirmation dialogs, form validation, and image carousels. Hopefully these examples will help you better understand JavaScript applications.

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