title: Extract Javascript data using map(), filter() and concatAll() functions
body: <p>The output is almost correct, but I am having trouble flattening the nested boxart array. </p>
  
  <p><strong>Javascript data:</strong> </p>
  
  <pre><code>var movieLists = {
      name: "Instant Queue",
      videos : [
          {    
               "id": 70111470,
               "title": "Die Hard",
               "boxarts": [
                   {width: 150, height:200, url:"http://cdn-0.nflximg.com/images/2891/DieHard150.jpg"}, 
                   {width: 200, height:200, url:"http://cdn-0.nflximg.com/images/2891/DieHard200.jpg"}
               ],
              "url": "http://api.netflix.com/catalog/titles/movies/70111470",
              "rating": 4.0,
              "bookmark": [{ id:432534, time:65876586 }]
          },
          {
              "id": 654356453,
              "title": ....,
          }];
  </code></pre>
  
  <p><strong>Expected Output:</strong> (using only the functions<code>.map()</code>, <code>.filter()</code>, <code>.concatAll()</code>, return id, title, boxart:url of films which have the boxart image dimensions 150x200</p>
  
  <pre><code>// [
  //     {"id": 675465,"title": "Fracture","boxart":"http://cdn-0...." },
  //     {"id": 65432445,"title": "The Chamber","boxart":"http://cdn-0...." },
  //     {"id": 654356453,...}
  // ];
  </code></pre>
  
  <p><strong>Current Output:</strong></p>
  
  <pre><code>// [                                    //boxart value is an array
  //     {"id": 675465,"title": "Fracture","boxart":["http://cdn-0...."]},
  //     {"id": 65432445,"title": "The Chamber","boxart":["http://cdn-0...."]},
  //     {"id": 654356453,...}
  // ];
  </code></pre>
  
  <p><strong>My Solution</strong>:</p>
  
  <pre><code>return movieLists.map(function (category) {
     return category.videos.map(function (video) {
         return {
             id: video.id,
             title: video.title,
             boxart: video.boxarts.filter(function (boxartFeature) {
                 return boxartFeature.width === 150 &amp;&amp; boxartFeature.height === 200;
             })
                 .map(function (boxartProp) {
                 return boxartProp.url;
             })
         };
     });
   }).concatAll(); //Flattens nested array by 1 dimension (please see demo)
  </code></pre>
  
  <p>I know I need to apply the <code>.concatAll()</code> function to remove the nested boxart array, but I can't seem to find the place where. </p>
  
  <p>Please click <a href="https://jsbin.com/tirapi/edit?js,console" rel="nofollow">here for demo</a> </p>