title: Nicer way to optionally include String in ES6 String template
body: <p>I want to display <strong>hello username</strong> if a condition <code>isLoggedIn</code> is true, and just <strong>hello</strong> otherwise.</p>
  
  <p>I'm using ES6 String templates to try to make the syntax nicer than plain old string concatenation. However the best way I've found to do it is the following (<a href="http://www.es6fiddle.net/igo1lwrq/" rel="noreferrer">es6fiddle</a>)</p>
  
  <pre><code>`hello ${isLoggedIn(false) ? username : ''}`
  </code></pre>
  
  <p>It's still not very nice syntax, particularly in longer templates where there is more than one variable I want to do this with.</p>
  
  <p>I have been trying to find a syntax which includes strings optionally into templates, based on a condition, but I don't think there is one. Something like this would be nicer:</p>
  
  <pre><code>`hello ${condition &amp;&amp; username}`
  </code></pre>
  
  <p>But, it renders <strong>false</strong> into the String if the condition is false. </p>
  
  <p>I also tried baking the truthiness of <code>username</code> into the variable itself, i.e. have <code>username</code> be <code>undefined</code> or <code>null</code> if it doesn't exist - however the string template then just renders <strong>undefined</strong> or <strong>null</strong>.</p>
  
  <p><strong>Can anyone recommend a nicer syntax, or approach, or is the first method the best I'm going to do with String templates?</strong></p>