javascript实现的功能实例有哪些-前端问答-PHP中文网

javascript实现的功能实例有哪些

PHPz

发布： 2023-04-21 14:16:22

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javascript是一种常用的脚本语言，被广泛用于网页交互性设计和开发。今天，我们将介绍一些javascript实现的实用功能实例。

简单的计算器

JavaScript可用于创建简单的计算器。该代码段使用HTML中的按钮和输入框，以及JavaScript处理计算器的逻辑。用户输入数字、操作符和操作数，然后点击等于号运行计算并显示结果。

<!DOCTYPE html>
<html>
   <head>
      <meta charset="UTF-8">
      <title>Simple Calculator</title>
   </head>
   <body>
      <form name="calculator">
         <input type="text" name="answer" id="answer">
         <br>
         <input type="button" value=" 1 " onclick="calculator.answer.value += '1'">
         <input type="button" value=" 2 " onclick="calculator.answer.value += '2'">
         <input type="button" value=" 3 " onclick="calculator.answer.value += '3'">
         <input type="button" value=" + " onclick="calculator.answer.value += '+'">
         <br>
         <input type="button" value=" 4 " onclick="calculator.answer.value += '4'">
         <input type="button" value=" 5 " onclick="calculator.answer.value += '5'">
         <input type="button" value=" 6 " onclick="calculator.answer.value += '6'">
         <input type="button" value=" - " onclick="calculator.answer.value += '-'">
         <br>
         <input type="button" value=" 7 " onclick="calculator.answer.value += '7'">
         <input type="button" value=" 8 " onclick="calculator.answer.value += '8'">
         <input type="button" value=" 9 " onclick="calculator.answer.value += '9'">
         <input type="button" value=" * " onclick="calculator.answer.value += '*'">
         <br>
         <input type="button" value=" c " onclick="calculator.answer.value = ''">
         <input type="button" value=" 0 " onclick="calculator.answer.value += '0'">
         <input type="button" value=" = " onclick="calculator.answer.value = eval(calculator.answer.value)">
         <input type="button" value=" / " onclick="calculator.answer.value += '/'">
         <br>
      </form>
   </body>
</html>

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倒计时器

JavaScript可用于创建倒计时器，即从指定的日期和时间开始倒计时，直到特定目标时间。该代码段使用Date对象来获取当前时间和目标时间，计算差异，并将其显示在HTML页面上。

<!DOCTYPE html>
<html>
   <head>
      <meta charset="UTF-8">
      <title>CountDown Timer</title>
   </head>
   <body>
      <div id="countdown"></div>
      <script>
         // Set the date we're counting down to
         var countDownDate = new Date("Jan 1, 2022 00:00:00").getTime();
         // Update the count down every 1 second
         var x = setInterval(function() {
             // Get today's date and time
             var now = new Date().getTime();
             // Find the distance between now and the count down date
             var distance = countDownDate - now;
             // Time calculations for days, hours, minutes and seconds
             var days = Math.floor(distance / (1000 * 60 * 60 * 24));
             var hours = Math.floor((distance % (1000 * 60 * 60 * 24)) / (1000 * 60 * 60));
             var minutes = Math.floor((distance % (1000 * 60 * 60)) / (1000 * 60));
             var seconds = Math.floor((distance % (1000 * 60)) / 1000);
             // Output the result in an element with id="countdown"
             document.getElementById("countdown").innerHTML = days + "d " + hours + "h "
             + minutes + "m " + seconds + "s ";
             // If the count down is over, write some text 
             if (distance < 0) {
                 clearInterval(x);
                 document.getElementById("countdown").innerHTML = "EXPIRED";
             }
         }, 1000);
      </script>
   </body>
</html>

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图片轮播器

JavaScript可用于创建图片轮播器，其中一组图像轮流显示在网页上。该代码段使用HTML中的图像元素和JavaScript逻辑，用数组存储图像列表，并在指定的时间间隔内更新当前图像。

<!DOCTYPE html>
<html>
   <head>
      <meta charset="UTF-8">
      <title>Image Slider</title>
   </head>
   <body>
      <div id="slider">
         <img id="sliderImg" src="">
      </div>
      <script>
         var images = [
             "img1.jpg", "img2.jpg", "img3.jpg", "img4.jpg"
         ];
         var current = 0;
         function changeImage(){
             current++;
             if(current >= images.length){
                 current = 0;
             }
             document.getElementById("sliderImg").src = images[current];
         }
         setInterval(changeImage, 3000);
      </script>
   </body>
</html>

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表单验证

JavaScript可用于验证用户输入，以确保输入数据的格式和内容正确。该代码段使用HTML表单元素和JavaScript逻辑，通过检查每个表单元素来验证用户输入。

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<!DOCTYPE html>
<html>
   <head>
      <meta charset="UTF-8">
      <title>Form Validation</title>
      <style>
         .error{
             color: red;
         }
      </style>
   </head>
   <body>
      <form id="myForm">
         <label for="name">Name:</label>
         <input type="text" id="name" name="name"><br>
         <label for="email">Email:</label>
         <input type="email" id="email" name="email"><br>
         <label for="phone">Phone:</label>
         <input type="text" id="phone" name="phone"><br>
         <input type="submit" value="Submit">
      </form>
      <script>
         document.getElementById("myForm").addEventListener("submit", function(event){
             var name = document.getElementById("name").value;
             var email = document.getElementById("email").value;
             var phone = document.getElementById("phone").value;
             var nameError = document.getElementById("nameError");
             var emailError = document.getElementById("emailError");
             var phoneError = document.getElementById("phoneError");
             if(!name){
                 nameError.innerHTML = "Please enter your name.";
                 event.preventDefault();
             }
             if(!email){
                 emailError.innerHTML = "Please enter your email.";
                 event.preventDefault();
             }
             if(!phone){
                 phoneError.innerHTML = "Please enter your phone number.";
                 event.preventDefault();
             }
         });
      </script>
   </body>
</html>

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总结

这些是JavaScript实现的功能实例，涵盖了计算器、倒计时器、图片轮播器和表单验证等实用功能。当然，这只是JavaScript应用功能的冰山一角，JavaScript在Web设计和开发中有着很多其他用途和应用场景。

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