title: how to trigger angular strap bs-select programmatically
body: <p>I'm using angularstrap's bs-select to do a drop down list select. And I want to programmatically trigger the drop down list button with JavaScript. 
  Here is the plunker:</p>
  
  <p><a href="http://plnkr.co/edit/dQsW6j817pdB2YpXuxU2?p=preview" rel="nofollow">Plunker Link</a></p>
  
  <p>I want to use the button to trigger the drop down list. I've tried three methods:</p>
  
  <ol>
  <li><code>angular.element(document.querySelector("#test1")).triggerHandler('click');</code> </li>
  </ol>
  
  <p>it works with the elements with <code>ng-click</code>. But didn't work in <code>bs-select</code></p>
  
  <ol start="2">
  <li><code>document.getElementById("test1").click();</code></li>
  </ol>
  
  <p>still didn't work for the <code>triggerHandler('click')</code></p>
  
  <ol start="3">
  <li><code>angular.element(document.querySelector("#test1")).triggerHandler('click');
  $scope.$apply()</code></li>
  </ol>
  
  <p>I thought it would be the problem that the scope need to digest again but it turns out that that is not the case.  </p>
  
  <p>And in angular strap the bs-select code is as follows:</p>
  
  <pre><code>$select.$onMouseDown = function(evt) {
      // Prevent blur on mousedown on .dropdown-menu
      evt.preventDefault();
      evt.stopPropagation();
      // Emulate click for mobile devices
      if(isTouch) {
          var targetEl = angular.element(evt.target);
          targetEl.triggerHandler('click');
      }
  };
  </code></pre>
  
  <p>When it's mousdown it trigger the click on this button. So how can I do with it?</p>
  
  <p>Thanks for the reply.</p>