title: FOR loop and string concatenating with JavaScript gives me an undefined value
body: <p>I have the array</p>
  
  <pre><code>var data = [name, address, city, country];
  </code></pre>
  
  <p>And the loop</p>
  
  <pre><code>var columns;
  for (var i = 0; i &lt; data.length; i++) {
      columns += "data[" + i + "], ";
  }
  columns = columns.slice(0, -2);
  alert(columns);
  </code></pre>
  
  <p>The alert message says </p>
  
  <pre><code>undefineddata[0], data[1], data[2], data[3]
  </code></pre>
  
  <p>What am I doing wrong here? I want to remove the undefined...</p>