问题
If the pdf viewer plugin is not installed how to detect it and give a alert message to install pdf viewer
回答1:
I created a script on my blog for all major browsers to detect pdf reading capabilities. Even distinguishes between Chrome's PDF Viewer and Acrobat. you can get the code here:
Detecting Adobe Acrobat in all browsers
来源：https://stackoverflow.com/questions/4122061/javascript-detect-adobe-reader-plugin-for-browser