Download plugins by javascript on Chrome, Safari

I have implemented the plugin by NPAPI for Firefox, Chrome, Safari, but there is a issue for me is how to download the plugin by JavaScript on Chrome, Safari?

I know the .xpi is a extension for Firefox, and I can write the script for downloading the xpi from server and Firefox will equip a xpi to Firefox extension folder.

But how can Chrome and Safari do for downloading the plugin ? As I know the Chrome should put its plugin dll on C:\Users\UserNa开发者_开发百科me\AppData\Local\Google\Chrome\Application\plugins folder, Safari should put its C:\Program Files\Safari\Plugins?

I'm appreciated for any infomation. Thanks

Why not do 'document.location = pluginurl' or "googlechrome.exe pluginurl"