title: Grails: PrototypeJS lib adding an extra underscore (_) parameter and doubling up all parameters
body: <p>I'm using <code>Grails 2.3.3</code> with prototype as my js library.</p>
  
  <p>I have an ajax call that sends over some parameters to the server that are to be bound to an object.
  The ajax call that is generated always appends <code>&amp;_:</code> at the end of my parameter list. So instead of having this map: <code>[name:bar, action:save, controller:foo]</code> I get <code>[name:bar, _:, action:save, controller:foo]</code> (note the <code>_:</code>)</p>
  
  <p>When I try to do
  <code>foo.properties = params</code>
  I get the following error (on <code>foo.errors</code>):</p>
  
  <pre><code>grails.validation.ValidationErrors: 1 errors
  Error in object 'com.mypackage.Foo': codes []; arguments []; default message [String index out of range: 2]
  End of error dump
  </code></pre>
  
  <p>If I remove the appended <code>_</code> key from the parameter map (with <code>params.remove('_')</code>) it no longer has errors.</p>
  
  <p>The problem here is that this worked fine on my app with Grails version 1.3.9 but it stopped working once I made the upgrade to 2.3.3.</p>
  
  <hr>
  
  <p>After upgrading prototype library, the parameters are now doubled up.</p>