title: Why binding to null not work when value of number input illegal in AngularJs
body: <p>See example here: <a href="https://jsfiddle.net/codefalling/u2mn764x/1/" rel="nofollow">https://jsfiddle.net/codefalling/u2mn764x/1/</a></p>
  
  <pre><code>&lt;div ng-app&gt;
    &lt;div ng-controller="TodoCtrl"&gt;
        &lt;input type="number" ng-model="value"  size="30" &gt;
        &lt;input type="button" ng-click="change()" class="btn-primary" value="TEST" &gt;
    &lt;/div&gt;
  &lt;/div&gt;
  
  function TodoCtrl($scope) {
    $scope.change = function() {
      $scope.value = null
    }
  }
  </code></pre>
  
  <p>When I type <code>10</code> into number input, click button, it turn to be empty.</p>
  
  <p>However when I type a standalone <code>e</code> or <code>.</code> into number input, then click button, nothing happend. But <code>$scope.value = 123</code> stills works.</p>
  
  <p>So, <strong>Why view didn't get update(empty) in this situation</strong>?</p>
  
  <p>Additional, is there any other way to empty it?</p>