JS添加版本号

 <script>
    var value= new Date().getTime();
    var versionStamp = sessionStorage.version;
    if (versionStamp == null || (value- versionStamp) > 1800000) {
        sessionStorage.version = value;
    }
    document.write("<script src='../js/chat.js?v=" + sessionStorage.version + "'><" + '/' + "script>");
</script>

解决更改JS代码、需要清除浏览器缓存的问题