Design Thoughts
The key to this method is the comprehensive use of cookie technology and dynamic image characteristics. Using cookies, the user's data can be recorded on the user's hard drive. The next time you visit this site, you can read the cookie on the user's hard drive and directly learn the visitor's identity, number of visits, and other relevant information. Cookies are accessed in JavaScript through the document.cookie attribute, which includes name, expiration date, valid domain name, valid URL path, etc. The name and its value separated by an equal sign are the actual data of the cookie, which in this case is used to store the number of times the visitor visited the page. By mapping the images in the Web page to an Images array and modifying the characteristics of the array items under certain conditions, dynamic image display can be achieved. In this example, a set of images is first preloaded. Each time the Web page is called, a new set of images is randomly generated, and a dynamic and interesting effect is achieved by overwriting the original images.
Source program count.html
< html> < head> < meta http-equiv=″Content-Type″ content=″text/html; charset=gb2312″> < title>趣味计数器< /title> < /head> < body> < p>< script language=″JavaScript″> var expdays=60; var exp=new Date(); exp.setTime(exp.getTime() (expdays*24*60*60*1000)); function count(info){ //若是该访客的第一次访问,将计数器值赋1,否则加1累积 var wwhcount=getcookie(′wwhcount′); if (wwhcount==null){ wwhcount=1; } else{wwhcount++;} setcookie(′wwhcount′,wwhcount,exp); return countdisp(wwhcount) } function countdisp(countvar){ //实现随机显示,不足6位以0补全,可以自己调整显示位数 var countvar1=″000000″+countvar; var howFar1=countvar1.length; countvar1=countvar1.substring(howFar1, howFar1-1) var index=″ ″+Math.floor(Math.random()*10); if (index==″10″){ index=″0″}; for (var icount=0;icount< 6;icount++){ var g=countvar1.substring(icount,icount+1); document.images[icount].src=″http: //localhost/images/″+index+g+″.gif″; } } function getCookieVal(offset){ //获取该访问者的已访问次数 var endstr=document.cookie.indexOf(″;″,offset); if (endstr==-1) endstr=document.cookie.length; return unescape(document.cookie.substring(offset,endstr)); } function getcookie(name){ //截取Cookie中的name信息段 var arg=name+″=″; var alen=arg.length; var clen=document.cookie.length; var i=0; while (i< clen){ var j=i+alen; if (document.cookie.substring(i,j)==arg) return getCookieVal(j); i=document.cookie.indexOf(″ ″,i)+1; if (i==0) break;} return null; } function setcookie(name,value){ //存储该访客计数器的数值 var argv=setcookie.arguments; var argc=setcookie.arguments.length; var expires=(argc>2)?argv[2]:null;var path=(argc>3)?argv[3]:null; var domain=(argc>4)?argv[4]:null; var secure=(argc〉5)?argv[5]:false; document.cookie=name+″=″+escape(value) +((expires==null)?″ ″:(″;expires=″+expires.toGMTString())) +((path==null)?″ ″:(″;path=″+path))+((domain==null)?″ ″:(″;domain=″+domain))+((secure==true)?″;secure″:″ ″); } function deletecookie(name){ //使该信息行失效,删除该用户关于访问次数的信息 var exp=new Date(); exp.setTime(exp.getTime()-1); var cval=getcookie(name); document.cookie=name+″=″+cval+″;expires=″+exp.toGMTString(); } < /script>< /p> < ! --预载入图像数组--> 您是第 < img src=″http://localhost/images/00.gif″ height=20 width=20> < img src=″http://localhost/images/00.gif″ height=20 width=20> < img src=″http://localhost/images/00.gif″ height=20 width=20> < img src=″http://localhost/images/00.gif″ height=20 width=20> < I mg src=″http://localhost/images/00.gif″ height=20 width=20> < img src=″http://localhost/images/00.gif″ height=20 width=20>次光临! < script language=″JavaScript″> //调用count()函数,实现计数器的动态图像显示 count(); < /script> < /body> < /html>
Things to note
Since the JavaScript language is used, this method is independent of the application platform and can be applied to Unix, Windows and other platforms. In addition, this counter is different from the general visitor counter and is specifically used to record the number of times a visitor visits a certain website.

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 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 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.

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 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.

C and C play a vital role in the JavaScript engine, mainly used to implement interpreters and JIT compilers. 1) C is used to parse JavaScript source code and generate an abstract syntax tree. 2) C is responsible for generating and executing bytecode. 3) C implements the JIT compiler, optimizes and compiles hot-spot code at runtime, and significantly improves the execution efficiency of JavaScript.

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.

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.


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