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Reference JavaScript Code Library

Plug-ins can be great if the person visiting your Web page has them installed. But if they're not installed, your user will be presented with a nasty-looking broken link icon. The trick is detecting whether or not they're installed before attempting to serve the plug-in content.

There's no perfect way to detect plug-ins, but the code on this page does it's damnedest to find out what's installed and what's not. There are two ways to use the code, both of which are explained below. Each will return a value of true (if the plug-in is there) or false (if it isn't there or if there's no way to tell). As Meghan's article points out, in some circumstances, plug-ins are just undetectable.

Usage: There are two ways to use WM_pluginbot — the easy (basic) way and the hard (advanced) way.

The Basic Way
If all you need to know is whether the user has some version of the Flash, QuickTime, Shockwave, or RealAudio plug-in, you can use the helper function WM_easyDetect and just tell it which plug-in to look for, like so:

: WM_easyDetect('flash');
: WM_easyDetect('quicktime');
: WM_easyDetect('shockwave');
: WM_easyDetect('realaudio');

You can then use this information to send the user to a different page depending on the result:

: var hasFlash = WM_easyDetect('flash'); if(hasFlash) { window.location = 'flashversion.html'; } else { window.location = 'noflashversion.html'; }

If you're confused, take a look at the source code on the demo page.

The Advanced Way
If you need to check for a specific version (such as Flash version 4) or a plug-in other than these four, you'll need to use the main WM_pluginbot function and give it four arguments:

: WM_pluginBot('pluginDescription' , 'fileExtension' , 'mimeType' , 'activeXControl' );

You can find out the pluginDescription by choosing Help/About Plug-ins in Netscape Navigator. Internet Explorer doesn't list plug-ins, so you'll have to use the name of the ActiveX control. Finding these names can be difficult; your best bet is to check with the plug-in manufacturer. You can leave the activeXControl blank (by inserting double quote marks), but this will return a value of false for Internet Explorer, even if the plug-in is installed.

This may seem a bit complicated (which is why we added the WM_easyDetect shortcut), but you can get a better idea of how it works by taking a look at the source code on the demo page.

License: Webmonkey Public License

Cut, paste, and enjoy!

/*
Plugin Detector()

Source: Webmonkey Code Library
(http://www.hotwired.com/webmonkey/javascript/code_library/)

Author: Nadav Savio
Author Email: webmonkey@giantant.com

// this is where we write out the VBScript for MSIE Windows
var WM_startTagFix = '</';
var msie_windows = 0;
if ((navigator.userAgent.indexOf('MSIE') != -1) && (navigator.userAgent.indexOf('Win') != -1)){
  msie_windows = 1;
  document.writeln('<script language="VBscript">');
  document.writeln('\'This will scan for plugins for all versions of Internet Explorer that have a VBscript engine version 2 or greater.');
  document.writeln('\'This includes all versions of IE4 and beyond and some versions of IE 3.');
  document.writeln('Dim WM_detect_through_vb');
  document.writeln('WM_detect_through_vb = 0');
  document.writeln('If ScriptEngineMajorVersion >= 2 then');
  document.writeln('  WM_detect_through_vb = 1');
  document.writeln('End If');
  document.writeln('Function WM_activeXDetect(activeXname)');
  document.writeln('  on error resume next');
  document.writeln('  If ScriptEngineMajorVersion >= 2 then');
  document.writeln('     WM_activeXDetect = False');
  document.writeln('     WM_activeXDetect = IsObject(CreateObject(activeXname))');
  document.writeln('     If (err) then');
  document.writeln('        WM_activeXDetect = False');
  document.writeln('     End If');
  document.writeln('   Else');
  document.writeln('     WM_activeXDetect = False');
  document.writeln('   End If');
  document.writeln('End Function');
  document.writeln(WM_startTagFix+'script>');
}

function WM_pluginDetect(plugindescription, pluginxtension, pluginmime, activeXname){

//This script block will test all user agents that have a real plug-in array

//(i.e. Netscape) and set the variables, otherwise it directs the routine

// to WM_activeXDetect to detect the activeX control.

// First define some variables
  var i,plugin_undetectable=0,detected=0, daPlugin=new Object();

// Then we check to see if it's an MSIE browser that you can actually

// check for the plugin in question.

if (msie_windows && WM_detect_through_vb){
      plugin_undetectable = 0;
  } else {
      plugin_undetectable = 1;
  }

// If it has a real plugins or mimetypes array, we look there for the plugin first

if(navigator.plugins) {
      numPlugins = navigator.plugins.length;
      if (numPlugins > 1) {
	  if (navigator.mimeTypes && navigator.mimeTypes[pluginmime] && navigator.mimeTypes[pluginmime].enabledPlugin && (navigator.mimeTypes[pluginmime].suffixes.indexOf(pluginxtension) != -1)) { // seems like we have it, let's just make sure and check the version (if specified)
	      if ((navigator.appName == 'Netscape') && (navigator.appVersion.indexOf('4.0') != -1)) { // stupid, stupid Netscape can't handle the references to navigator.plugins by number, sooo...
		  for(i in navigator.plugins) {
		      if ((navigator.plugins[i].description.indexOf(plugindescription) != -1) || (i.indexOf(plugindescription) != -1)) { // some versions of quicktime have no description. feh!
			  detected=1;
			  break;
		      }
		  }
	      } else {
		  for (i = 0; i < numPlugins; i++) {
		      daPlugin = navigator.plugins[i];
		      if ((daPlugin.description.indexOf(plugindescription) != -1) || (daPlugin.name.indexOf(plugindescription) != -1)) {
			  detected=1;
			  break;
		      }
		  }
	      }

// Mac weirdness
      if (navigator.mimeTypes[pluginmime] == null) {
		  detected = 0;
	      }
	  }
	  return detected;
      } else if((msie_windows == 1) && !plugin_undetectable){
	  return WM_activeXDetect(activeXname);
      } else { 		
	  return 0;
      }
  } else {
      return 0;
  }
}

// this next function just makes it easy to detect the common plugins

function WM_easyDetect(whichPlugin) {

// this function just makes it easy to do basic plug-in detection without

// knowing all the mimetypes and activeX names and such
    var isItThere = 0;
    if( (whichPlugin == 'flash') || (whichPlugin == 'Flash') ) {
	isItThere = WM_pluginDetect('Flash', 'swf', 'application/x-shockwave-flash', 'ShockwaveFlash.ShockwaveFlash');
    } else if( (whichPlugin == 'director') || (whichPlugin == 'Director') ) {
	isItThere = WM_pluginDetect('Shockwave', 'dcr', 'application/x-director', 'SWCtl.SWCtl.1');
    } else if( (whichPlugin == 'quicktime') || (whichPlugin == 'Quicktime') || (whichPlugin == 'QuickTime') ) {
	isItThere = WM_pluginDetect('QuickTime', 'mov', 'video/quicktime', '');
    } else if( (whichPlugin == 'realaudio') || (whichPlugin == 'Realaudio') || (whichPlugin == 'RealAudio') ) {
	isItThere = (WM_pluginDetect('RealPlayer', 'rpm', 'audio/x-pn-realaudio-plugin', 'RealPlayer.RealPlayer(tm) ActiveX Control (32-bit)')) || (WM_pluginDetect('RealPlayer', 'rpm', 'audio/x-pn-realaudio-plugin','rmocx.RealPlayer G2 Control')) || (WM_pluginDetect('RealPlayer', 'rpm', 'audio/x-pn-realaudio-plugin','RealPlayer.RealPlayer(tm) ActiveX Control (32-bit)')) || (WM_pluginDetect('RealPlayer', 'rpm', 'audio/x-pn-realaudio-plugin','RealVideo.RealVideo(tm) ActiveX Control (32-bit)'))
    } else {

alert('You need to tell me which plug-in to look for, like so:\n\n' + '          WM_easyDetect(\'flash\')\n\n' + '          WM_easyDetect(\'director\')\n\n' + '          WM_easyDetect(\'quicktime\')\n\n' + '          WM_easyDetect(\'realaudio\')');
    }
    return isItThere;
}

// -->

</script>