title: jQuery .closest() returns multiple results within a custom jQuery plugin
body: <p>While hacking my free-time project I stumbled upon a puzzling jQuery behaviour.</p>
  
  <p>I have a custom validation plugin written and working. In the plugin I wanted to implement some functionality using .closest() method. Strangely enough this method returns multiple elements.</p>
  
  <p>Here is a sample code:</p>
  
  <pre><code>this.closest(".control-group")
  $(this).closest(".control-group");
  </code></pre>
  
  <p>Both above code lines select all four elements with class "control-group". This code put inside my plugin works:</p>
  
  <pre><code>var element_ID = this.attr("id");
  $("#" + element_ID).closest(".control-group")
  </code></pre>
  
  <p>Above selects the correct and only one element with "control-group" class.</p>
  
  <p>I can't use this "hack" as not all elements that I want to validate have "id" property set, so it won't work in all cases.</p>
  
  <p>Using jQuery 1.7.2 (seems to be latest stable). Any ideas why it's like that?</p>