title: jquery: check if string exist in element, return boolean
body: <p>Assuming I have this:</p>
  
  <p><code>&lt;div id="elementId"&gt;bla bla bla some text bla bla&lt;/div&gt;</code></p>
  
  <p>I want to check if this div text contains 'some text', then return true, otherwise return false, how to do that?</p>