Detecting BrowserPlus

This code sample demonstrates how you can detect whether BrowserPlus is installed.

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<html>
<head><title>What If BrowserPlus Isn't installed?</title></head>
<body>
Let's see if BrowserPlus is installed... 

<script src="http://bp.yahooapis.com/2.9.9/browserplus-min.js"></script>
<script class="javascript">
BrowserPlus.init(function(r) {
  function bplusInitialized() {
    // this function will be called when BrowserPlus is ready,
    // either after the user goes and installs it, or immediately if
    // BrowserPlus was already installed.

    // so... require some services!
  }

  if (r.success) {
    // BrowserPlus is installed and ready to go!
    alert("Yahoo! BrowserPlus installed, v" + BrowserPlus.getPlatformInfo().version);
    bplusInitialized();
  } else if (r.error == "bp.notInstalled") {
    // BrowserPlus isn't installed, but the client browser/operating system
    // is supported!  we can render a link to let our users know that
    // more features are available if they install the thing.
    BrowserPlus.initWhenAvailable({}, bplusInitialized);
    alert("Get BrowserPlus! You can do it!");
  } else if (r.error == "bp.unsupportedClient") {
    // Uh oh, they're running a browser we don't yet support.  We should
    // probably disable features that require browserplus, and rendering
    // an installation link for BrowserPlus is useless.
  } else {
    // yikes!  Unexpected error!
    throw(r.error + ": " + r.verboseError);
  }
});
</script>
</body>
</html>
Run Example

Inline comments describe the possible cases when you call BrowserPlus.init():

r.success === true
BrowserPlus is installed and ready to use
r.error === 'bp.notInstalled'
BrowserPlus is not installed and client platform is supported
r.error === 'bp.unsupportedClient'
BrowserPlus is not installed and client platform is NOT supported
otherwise
BrowserPlus encountered an error during initialization

The last two cases should be considered failure cases, and as a developer you should disable BrowserPlus functionality. In the second case you can render a link pointing to http://browserplus.yahoo.com/install, and describe to your user what features will become available to them if they install BrowserPlus. Further, if you would like to automatically detect when BrowserPlus is installed without a page reload you can use the BrowserPlus.initWhenAvailable() platform function which will set up a poller and once init() completes successfully, will invoke the callback you provide.

Using this handful of tools it should be possible to craft the precise experience you're looking for.