title: How to return the next indexOf after a previous?
body: <p>For example: </p>
  
  <pre><code>str = "(a+b)*(c+d)*(e+f)"
  str.indexOf("(") = 0
  str.lastIndexOf("(") = 12
  </code></pre>
  
  <p>How to get the index in second bracket? 
  (c+d) &lt;- this</p>