title: Insert a string at a specific index
body: <p>How can I insert a string at a specific index of another string? </p>
  
  <pre><code> var txt1 = "foo baz"
  </code></pre>
  
  <p>Suppose I want to insert "bar " after the "foo" how can I achieve that?</p>
  
  <p>I thought of <code>substring()</code>, but there must be a simpler more straight forward way.</p>