How to clear cache in javascript

How to clear the cache in javascript: 1. Clear the website cache through the meta method; 2. Use ajax to request the latest file from the server, and add the request headers "If-Modified-Since" and "Cache-Control"; 3. , directly use "cache:false" and so on.

The operating environment of this article: Windows 7 system, JavaScript version 1.8.5, DELL G3 computer.

Several methods of clearing JS cache

1. Why do CSS and JS have parameters (in the form of .css?t= and .js?t=) and how to obtain them Code

css and js with parameters (in the form of .css?t= and .js?t=)

There are two possibilities for using parameters:

First, the script does not exist, but is dynamically generated by the server, so a version number is included to show the difference. That is, the above code is equivalent to the file, but the browser will think it is a certain version of the file!

Second, the client will cache these css or js files, so every time after upgrading the js or css file and changing the version number, the client browser will re-download the new js or css file and refresh it. The role of sexual caching.

The second situation is the most common, or both may exist at the same time.

The version number can be a random number, or an incremental value, in the form of a large version or a small version, or written according to the generation time of the script, for example, it is accurate to the second when the script is generated, and 2.3. 3 is the method of large version and small version.

2. About browser cache

Browser cache, sometimes we need it, because it can improve website performance and browser speed, and improve website performance. But sometimes we have to clear the cache, because the cache may cause problems and some erroneous data may appear. For example, stock websites are updated in real time. Such websites do not need to be cached. Some websites are rarely updated, so it is better to have cache. Today we mainly introduce several methods to clear cache.

Several ways to clear the website cache

meta method

<META HTTP-EQUIV="pragma" CONTENT="no-cache"> 
<META HTTP-EQUIV="Cache-Control" CONTENT="no-cache, must-revalidate"> 
<META HTTP-EQUIV="expires" CONTENT="0">

Clean the temporary cache of the form [Recommended learning: js basic tutorial 】

Method 1: Use ajax to request the latest file from the server, and add the request headers If-Modified-Since and Cache-Control, as follows:

$.ajax({
     url:'www.haorooms.com',
     dataType:'json',
     data:{},
     beforeSend :function(xmlHttp){ 
        xmlHttp.setRequestHeader("If-Modified-Since","0"); 
        xmlHttp.setRequestHeader("Cache-Control","no-cache");
     },
     success:function(response){
         //操作
     }
     async:false
  });

Method 2, use cache directly :false,

$.ajax({
     url:'www.haorooms.com',
     dataType:'json',
     data:{},
     cache:false, 
     ifModified :true ,
     success:function(response){
         //操作
     }
     async:false
  });

Method 3: Use random numbers. Random numbers are also a very good way to avoid caching!

Add "?ran=" Math.random(); //Of course the parameter ran here can be chosen arbitrarily

eg:

<script> 
document.write("<s"+"cript type=&#39;text/javascript&#39; src=&#39;/js/test.js?"+Math.random()+"&#39;></scr"+"ipt>"); 
</script>

Others are similar , just add Math.random() after the address

Note: Because Math.random() can only work under Javascript, it can only be called through Javascript

Method 4: Use random time, the same as random numbers.

Add "?timestamp=" new Date().getTime(); after the URL parameters

Use PHP backend to clean up

Add header(" on the server side Cache-Control: no-cache, must-revalidate"); etc. (such as in php)

Method 5:

5, window.location.replace("WebForm1.aspx") ;

The parameter is the page you want to cover. The principle of replace is to replace the page specified by the replace parameter with the current page.

This prevents the user from clicking the back key. The javascript script is used, for example:

a.html

The following is a quotation fragment:

<html> 
     <head> 
         <title>a</title>      
         <script language="javascript"> 
             function jump(){ 
                 window.location.replace("b.html"); 
             } 
         </script> 
     </head> 
     <body> 
        <a href="javascript:jump()">b</a> 
    </body> 
</html>

b.html

The following is a quotation fragment:

<html> 
     <head> 
         <title>b</title>      
         <script language="javascript"> 
             function jump(){ 
                 window.location.replace("a.html"); 
             } 
         </script> 
     </head> 
     <body> 
        <a href="javascript:jump()">a</a> 
    </body> 
</html>

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