title: JSONata query to flatten array of arrays
body: <p>The JSONata doc <a href="http://docs.jsonata.org/basic.html#top-level-arrays-nested-arrays-and-array-flattening" rel="nofollow noreferrer">"top-level-arrays-nested-arrays-and-array-flattening"</a> covers the "flatten" case of an array of objects, each of which contains a property that contains an array value. </p>
  
  <p>However, I have not been able to figure out how to flatten an array of arrays. </p>
  
  <p>Q: What is the JSONata query to flatten an array of arrays? </p>
  
  <p>input</p>
  
  <pre><code>    [ [1,2], [], [3] ]
  </code></pre>
  
  <p>desired</p>
  
  <pre><code>    [ 1, 2, 3 ]
  </code></pre>