title: String concatenation : += operator versus string array joined
body: <p>The concatenation in many language using the <code>+=</code> operator create a new string instance. It is preffered to use a <code>string[]</code> that we join at the end.</p>
  
  <p>In Javascript :</p>
  
  <pre><code>var myString = new Array("Hello");
  myString.push(" ");
  myString.push("world !");
  console.log(myString.join(''));
  </code></pre>
  
  <p>is more efficient that :</p>
  
  <pre><code>var myString = "Hello";
  myString += " ";
  myString += "world !";
  console.log(myString);
  </code></pre>
  
  <p>In C#, does the <code>+=</code> operator create a new string ?
  Is the StringBuilder more efficient that using a <code>string[]</code> ?</p>