title: Find first index of a string after index
body: <p>I have a string: "www.google.com.sdg.jfh.sd"</p>
  
  <p>I want to find the first ".s" string that is found after "sdg".</p>
  
  <p>so I have the index of "sdg", by:</p>
  
  <pre><code>var start_index = str.indexOf("sdg");
  </code></pre>
  
  <p>now I need to find the first ".s" index that is found after "sdg"</p>
  
  <p>any help appreciated!</p>