$.alert is not a function

提示这个是为什么呢？我先引入jQuery了，也先定义消息了，代码如下

 var message = 'To use voice/video functions, you need to run Agora Media Agent first.<ul><li> If you do not have it installed, please visit url <a style="font-weight:bold;" href="' + err.agentInstallUrl + '">AgoraWebAgent</a> to install it. Please refer to the <a style="font-weight:bold;" href="' + err.agentInstallGuideUrl + '">installation guide</a> if you encounter any questions.</li><li>If you have installed it, please double click the icon to run this app.</li><li>If it has been running, please check if the internet connection is working or not.</li></ul>';
$.alert(message);

执行到这就提示出错

jquery没有alert这个方法。。其他js代码扩展的要一起倒入js文件

直接用window.alert(message);