AngularJS Example

HTML

<div ng-app="exapleOfFilter">
  <div ng-controller="Ctrl">
    <input ng-model="greeting" type="greeting">
      <br><br>
      <h1>{{greeting|isHello}}</h1>
  </div>
</div>

JavaScript

angular.module('exapleOfFilter', []).
  filter('isHello', function() {
    return function(input) {
      // conditional you want to apply
      if (input === 'hello') {
        return input;
      }
      return '';
    }
  });

function Ctrl($scope) {
  $scope.greeting = 'hello';
}