title: AngularJS filter multiple values if at least one of them is empty
body: <p>I'm using a filter to evaluate a couple of strings. If both of them are defined, I want to display them</p>
  
  <blockquote>
    <p>string0 string1</p>
  </blockquote>
  
  <p>else, I want to display a message like this:</p>
  
  <blockquote>
    <p>at least one of the strings is empty</p>
  </blockquote>
  
  <p>Here there is my filter</p>
  
  <pre><code>.filter('getStrsOrNoData', function () {
      return function (s0, s1) {
          if (s0 &amp;&amp; s1 ) {
              return s0 + ' ' + last;
          } else {
              return 'at least one of the strings is empty';
          }
      };
  })
  </code></pre>
  
  <p>and here is how I declare it in HTML, passing in 2 arguments:</p>
  
  <pre><code>&lt;p&gt;{{string1 + string2 | getStrsOrNoData : string1 : string2 }}&lt;/p&gt;
  </code></pre>
  
  <p>My problem is that when <code>s0 &amp;&amp; s1</code> is true, the displayed value is</p>
  
  <blockquote>
    <p>string0string1 string0</p>
  </blockquote>
  
  <p>I think the problem is <code>string1 + string2</code> but I don't know how to state two vars on the left side of the pipe....</p>