title: Filtering a multifaceted array, but the pipe return an error - Cannot find a differ supporting object '[object Object]' of type 'object'
body: <p>I am trying to filter output, but one field in the array is an array.</p>
  
  <p>When I'am filter all - I get all. 
  If I filter for any subset, the console.log(items[i].tags) output in array foramat <code>["Skills", "Learning"]</code>. 
  The 2nd console.log displays the item in the array (with both tags)</p>
  
  <p>The return throws the error: </p>
  
  <p><code>ERROR Error: Cannot find a differ supporting object '[object Object]' of type 'object'.  NgFor only supports binding to Iterables such as Arrays.
      at NgForOf.push../node_modules/@angular/common/fesm5/common.js.NgForOf.ngDoCheck</code></p>
  
  <p>...   in the HTML:</p>
  
  <pre><code>&lt;span *ngFor="let page of page | tags: tag  ; #nGForArray&gt;
  </code></pre>
  
  <p>...   The page array</p>
  
  <pre><code>[ { 
          "id" : "1", 
          "title" : "Security",  
          "tags" : ["Skills", "Learning"]
      },
  { 
          "id" : "2", 
          "title" : "Home Improvement",  
          "tags" : ["Skills"]
      },
  
  { 
          "id" : "3", 
          "title" : "Mathematics",  
          "tags" : [""Learning"]
      }
  ]
  </code></pre>
  
  <p>...   in search.pipe.ts</p>
  
  <pre><code>export class TagPipe implements PipeTransform {
  
      transform(items: any[], tag: string): any {
  
          if (!items || !tag) {
              return items;
          }
  
          var filtertags: any[];
  
          for (let i = 0; i &lt; items.length; i++) {
              console.log(items[i].tags);
              for (let j = 0; j &lt; items[i].tags.length; i++) {
                  if (tag == items[i].tags[j]) {
                      console.log(items[i]);
                      return items[i];
                  }
              }
  
          }
          console.log("end of transform");
          console.log(filtertags);
          return filtertags;
  
      }
  
  }
  </code></pre>
  
  <p>I need the results to find any record where one of the tags matches the filter.</p>