How is the JavaScript rebound animation effect implemented?-JS Tutorial-php.cn

Home

Web Front-end

JS Tutorial

How is the JavaScript rebound animation effect implemented?

零下一度

Jul 16, 2017 pm 03:25 PM

javascriptjshow

JavaScriptHow is the rebound animation effect achieved? Let me introduce it to you in detail through the code.

The code is as follows:

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    #box{
      width:200px;
      height:200px;
      position: absolute;
      top:0;
      left:200px;
      background:lightblue;
    }
    .btn{
      position:absolute;
      top:200px;
      left:100px;
      height:50px;
    }
    .btn input{
      display:inline-block;
      margin-left:50px;
      outline: none;
      width:100px;
      height:50px;
      border:1px solid green;
      cursor:pointer;
    }
  </style>
</head>
<body>
  <p id=&#39;box&#39;></p>
  <p class=&#39;btn&#39;>
    <input type="button" value=&#39;向左&#39; id=&#39;btnLeft&#39;>
    <input type="button" value=&#39;向右&#39; id=&#39;btnRight&#39;>
  </p>
  <script>
    var oBox = document.getElementById("box");
    var minLeft = 0;
    var maxLeft = utils.win(&#39;clientWidth&#39;)-oBox.offsetWidth;
    var step = 5;
    var timer = null;
    function move(target){
      //target:告诉我要运动的目标位置
      window.clearTimeout(timer);
      var curLeft = utils.css(oBox,"left");
      if(curLeft<target){//向右走
        if(curLeft+step>target){//边界
          utils.css(oBox,"left",target);
          return;
        }
        curLeft+=step;
        utils.css(oBox,"left",curLeft)
      }else if(curLeft>target){//向左走
        if(curLeft-step<target){//边界
          utils.css(oBox,"left",target);
          return;
        }
        curLeft-=step;
        utils.css(oBox,"left",curLeft)
      }else{//不需要运动
        return;
      }
      // timer = window.setTimeout(move,10)//这里有一个问题，点击按钮第一次target的值是有的，但是第二次通过setTimeout执行的时候没有给target进行传值。是undefined
      timer = window.setTimeout(function(){
        move(target);
      },10)//这样使用匿名函数包裹一下，就解决了上面的问题，但是这样写性能不好，因为每一次到达时间的时候，都需要执行一次匿名函数（形成一个私有的作用域）,在匿名函数中再执行move，但是move中需要用到的数据值在第一次执行的move方法中，需要把匿名函数形成的这个私有的作用域作为跳板找到之前的，这样就导致了匿名函数形成的这个私有的作用域不能销毁
    }
    document.getElementById(&#39;btnLeft&#39;).onclick = function(){
      move(minLeft)
    }
    document.getElementById(&#39;btnRight&#39;).onclick = function(){
      move(maxLeft)
    }
  </script>
</body>
</html>

In order to solve the above problem of poor performance, the following is an optimized code: it uses a function wrapper, so that there is only a private function created by the move function The domain is not destroyed. When _move is executed, move will naturally be destroyed.

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    #box{
      width:200px;
      height:200px;
      position: absolute;
      top:0;
      left:200px;
      background:lightblue;
    }
    .btn{
      position:absolute;
      top:200px;
      left:100px;
      height:50px;
    }
    .btn input{
      display:inline-block;
      margin-left:50px;
      outline: none;
      width:100px;
      height:50px;
      border:1px solid green;
      cursor:pointer;
    }
  </style>
</head>
<body>
  <p id=&#39;box&#39;></p>
  <p class=&#39;btn&#39;>
    <input type="button" value=&#39;向左&#39; id=&#39;btnLeft&#39;>
    <input type="button" value=&#39;向右&#39; id=&#39;btnRight&#39;>
  </p>
  <script>
    var oBox = document.getElementById("box");
    var minLeft = 0;
    var maxLeft = utils.win(&#39;clientWidth&#39;)-oBox.offsetWidth;
    var step = 5;
    var timer = null;
    function move(target){
      //target:告诉我要运动的目标位置
      _move();
      function _move(){
        window.clearTimeout(timer);
        var curLeft = utils.css(oBox,"left");
        if(curLeft<target){//向右走
          if(curLeft+step>target){//边界
            utils.css(oBox,"left",target);
            return;
          }
          curLeft+=step;
          utils.css(oBox,"left",curLeft)
        }else if(curLeft>target){//向左走
          if(curLeft-step<target){//边界
            utils.css(oBox,"left",target);
            return;
          }
          curLeft-=step;
          utils.css(oBox,"left",curLeft)
        }else{//不需要运动
          return;
        }
        timer = window.setTimeout(_move,10);
      }
    }
    document.getElementById(&#39;btnLeft&#39;).onclick = function(){
      move(minLeft)
    }
    document.getElementById(&#39;btnRight&#39;).onclick = function(){
      move(maxLeft)
    }
  </script>
</body>
</html>

Note: In order to allow the current element to run only one animation at the same time (first clear the timer of the previous animation when the next animation starts): ensure that the current element has all The variable that the animation receives the return value of the timer needs to be shared. There are two ways: 1. Global reception (for example, the above code var timer = null) 2. Add custom attributes to the element (as shown in the figure below)

Summary: From the above, we can draw four rules for animation optimization:

1. Boundary judgment and step size

2. Clear useless timers

　3. When the outer function needs to pass parameters, you can nest a layer of functions inside to avoid the accumulation of scopes.

　4. Store the return value of the timer in the custom attribute of the element to prevent global variable conflicts and multiple animation executions at the same time

The above is the detailed content of How is the JavaScript rebound animation effect implemented?. For more information, please follow other related articles on 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

Behind the Scenes: What Language Powers JavaScript?Apr 28, 2025 am 12:01 AM

JavaScript runs in browsers and Node.js environments and relies on the JavaScript engine to parse and execute code. 1) Generate abstract syntax tree (AST) in the parsing stage; 2) convert AST into bytecode or machine code in the compilation stage; 3) execute the compiled code in the execution stage.

The Future of Python and JavaScript: Trends and PredictionsApr 27, 2025 am 12:21 AM

The future trends of Python and JavaScript include: 1. Python will consolidate its position in the fields of scientific computing and AI, 2. JavaScript will promote the development of web technology, 3. Cross-platform development will become a hot topic, and 4. Performance optimization will be the focus. Both will continue to expand application scenarios in their respective fields and make more breakthroughs in performance.

Python vs. JavaScript: Development Environments and ToolsApr 26, 2025 am 12:09 AM

Both Python and JavaScript's choices in development environments are important. 1) Python's development environment includes PyCharm, JupyterNotebook and Anaconda, which are suitable for data science and rapid prototyping. 2) The development environment of JavaScript includes Node.js, VSCode and Webpack, which are suitable for front-end and back-end development. Choosing the right tools according to project needs can improve development efficiency and project success rate.

Is JavaScript Written in C? Examining the EvidenceApr 25, 2025 am 12:15 AM

Yes, the engine core of JavaScript is written in C. 1) The C language provides efficient performance and underlying control, which is suitable for the development of JavaScript engine. 2) Taking the V8 engine as an example, its core is written in C, combining the efficiency and object-oriented characteristics of C. 3) The working principle of the JavaScript engine includes parsing, compiling and execution, and the C language plays a key role in these processes.

JavaScript's Role: Making the Web Interactive and DynamicApr 24, 2025 am 12:12 AM

JavaScript is at the heart of modern websites because it enhances the interactivity and dynamicity of web pages. 1) It allows to change content without refreshing the page, 2) manipulate web pages through DOMAPI, 3) support complex interactive effects such as animation and drag-and-drop, 4) optimize performance and best practices to improve user experience.

C and JavaScript: The Connection ExplainedApr 23, 2025 am 12:07 AM

C and JavaScript achieve interoperability through WebAssembly. 1) C code is compiled into WebAssembly module and introduced into JavaScript environment to enhance computing power. 2) In game development, C handles physics engines and graphics rendering, and JavaScript is responsible for game logic and user interface.

From Websites to Apps: The Diverse Applications of JavaScriptApr 22, 2025 am 12:02 AM

JavaScript is widely used in websites, mobile applications, desktop applications and server-side programming. 1) In website development, JavaScript operates DOM together with HTML and CSS to achieve dynamic effects and supports frameworks such as jQuery and React. 2) Through ReactNative and Ionic, JavaScript is used to develop cross-platform mobile applications. 3) The Electron framework enables JavaScript to build desktop applications. 4) Node.js allows JavaScript to run on the server side and supports high concurrent requests.

Python vs. JavaScript: Use Cases and Applications ComparedApr 21, 2025 am 12:01 AM

Python is more suitable for data science and automation, while JavaScript is more suitable for front-end and full-stack development. 1. Python performs well in data science and machine learning, using libraries such as NumPy and Pandas for data processing and modeling. 2. Python is concise and efficient in automation and scripting. 3. JavaScript is indispensable in front-end development and is used to build dynamic web pages and single-page applications. 4. JavaScript plays a role in back-end development through Node.js and supports full-stack development.

See all articles