title: How to get the size of a filtered (piped) set in angular2
body: <p>I wrote my own filter pipe as it disappeared in angular2:</p>
  
  <pre><code>import {Pipe, PipeTransform} from 'angular2/core';
  
  @Pipe({
    name: 'myFilter'
  })
  export class MyFilter implements PipeTransform {
    transform(customerData: Array&lt;Object&gt;, args: any[]) {
      if (customerData == undefined) {
        return;
      }
      var re = new RegExp(args[0]);
      return customerData.filter((item) =&gt; re.test(item.customerId));
    }
  }
  </code></pre>
  
  <p>And use it in my template:</p>
  
  <pre><code>&lt;tr *ngFor="#singleCustomerData of customerData | myFilter:searchTerm"&gt;
    ...
  &lt;/tr&gt;
  </code></pre>
  
  <p>Now I'd like to see how many matches the pipe returns. So essentially the size of the returned array.</p>
  
  <p>In angular 1.x we were able so assign the returned set to a variable in a template like so:</p>
  
  <pre><code>&lt;div ng-repeat="person in filtered = (data | filter: query)"&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>But we can no longer assign variables in templates in angular2.</p>
  
  <p>So how do I get the size of the filtered set without calling the filter twice?</p>