title: Javascript, string interpolated function name
body: <p>I'm a javascript newbie.</p>
  
  <p>I have a line of code:</p>
  
  <pre><code>data.content_teaser.image_square_attachment_url
  </code></pre>
  
  <p>square can change: I have a variable called contentType that can be <code>'square'</code>, or <code>'vertical'</code> or <code>'horizontal'</code>.</p>
  
  <p>In ruby I can use send with the string interpolation, how can I obtain the same in js?</p>
  
  <p>Something like <code>"data.content_teaser.image_" + contentType + "_attachment_url"</code></p>