输入Angularjs number $ filter指令要求用户按两次十进制

Question

我试图将输入限制为仅限数字和小数，将分数大小固定为最大值2，并用逗号掩盖viewValue，并将modelValue保持为数字。下面的代码几乎完美无缺，除了为了添加小数，用户必须按两次.键。任何想法为什么第一次按下剥离小数？

var app = angular.module('myApp', []);
app.controller('pageCtrl', function($scope){
    $scope.myModel = 0;
});

app.directive('formatter', ['$filter', function ($filter) {
    return {
        require: '?ngModel',
        link: function (scope, elem, attrs, ctrl) {
            if (!ctrl || !attrs.formatter) return;
            ctrl.$formatters.unshift(function (a) {
                return $filter(attrs.formatter)(ctrl.$modelValue, 2)
            });

            ctrl.$parsers.unshift(function (viewValue) {
                var plainNumber = viewValue.replace(/[^0-9.]/g, '');
                var fractionSize = 0;
                if (plainNumber.indexOf('.') >= 0) {
                    var parts = plainNumber.split('.');
                    fractionSize = parts[1].length > 2 ? 2 : parts[1].length;
                }
                elem.val($filter(attrs.formatter)(plainNumber, fractionSize));

                return plainNumber;
            });
        }
    };
}]);

<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.23/angular.min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<body ng-app="myApp">
   <div ng-controller="pageCtrl">
      <input formatter="number" ng-model="myModel">
      {{ myModel }}
   </div>
</body>