function filterFilter() {
  return function(array, expression, comparator) {
    if (!isArray(array)) return array;

    var comparatorType = typeof(comparator),
        predicates = [];

    predicates.check = function(value) {
      for (var j = 0; j < predicates.length; j++) {
        if(!predicates[j](value)) {
          return false;
        }
      }
      return true;
    };

    if (comparatorType !== 'function') {
      if (comparatorType === 'boolean' && comparator) {
        comparator = function(obj, text) {
          return angular.equals(obj, text);
        };
      } else {
        comparator = function(obj, text) {
          if (obj && text && typeof obj === 'object' && typeof text === 'object') {
            for (var objKey in obj) {
              if (objKey.charAt(0) !== '$' && hasOwnProperty.call(obj, objKey) &&
                  comparator(obj[objKey], text[objKey])) {
                return true;
              }
            }
            return false;
          }
          text = (''+text).toLowerCase();
          return (''+obj).toLowerCase().indexOf(text) > -1;
        };
      }
    }

    var search = function(obj, text){
      if (typeof text == 'string' && text.charAt(0) === '!') {
        return !search(obj, text.substr(1));
      }
      switch (typeof obj) {
        case "boolean":
        case "number":
        case "string":
          return comparator(obj, text);
        case "object":
          switch (typeof text) {
            case "object":
              return comparator(obj, text);
            default:
              for ( var objKey in obj) {
                if (objKey.charAt(0) !== '$' && search(obj[objKey], text)) {
                  return true;
                }
              }
              break;
          }
          return false;
        case "array":
          for ( var i = 0; i < obj.length; i++) {
            if (search(obj[i], text)) {
              return true;
            }
          }
          return false;
        default:
          return false;
      }
    };
    switch (typeof expression) {
      case "boolean":
      case "number":
      case "string":
        // Set up expression object and fall through
        expression = {$:expression};
        // jshint -W086
      case "object":
        // jshint +W086
        for (var key in expression) {
          (function(path) {
            if (typeof expression[path] === 'undefined') return;
            predicates.push(function(value) {
              return search(path == '$' ? value : (value && value[path]), expression[path]);
            });
          })(key);
        }
        break;
      case 'function':
        predicates.push(expression);
        break;
      default:
        return array;
    }
    var filtered = [];
    for ( var j = 0; j < array.length; j++) {
      var value = array[j];
      if (predicates.check(value)) {
        filtered.push(value);
      }
    }
    return filtered;
  };
}
@ngdoc filter
@name filter
@kind function

@description
Selects a subset of items from `array` and returns it as a new array.

@param {Array} array The source array.
@param {string|Object|function()} expression The predicate to be used for selecting items from
  `array`.

  Can be one of:

  - `string`: The string is evaluated as an expression and the resulting value is used for substring match against
    the contents of the `array`. All strings or objects with string properties in `array` that contain this string
    will be returned. The predicate can be negated by prefixing the string with `!`.

  - `Object`: A pattern object can be used to filter specific properties on objects contained
    by `array`. For example `{name:"M", phone:"1"}` predicate will return an array of items
    which have property `name` containing "M" and property `phone` containing "1". A special
    property name `$` can be used (as in `{$:"text"}`) to accept a match against any
    property of the object. That's equivalent to the simple substring match with a `string`
    as described above.

  - `function(value)`: A predicate function can be used to write arbitrary filters. The function is
    called for each element of `array`. The final result is an array of those elements that
    the predicate returned true for.

@param {function(actual, expected)|true|undefined} comparator Comparator which is used in
    determining if the expected value (from the filter expression) and actual value (from
    the object in the array) should be considered a match.

  Can be one of:

  - `function(actual, expected)`:
    The function will be given the object value and the predicate value to compare and
    should return true if the item should be included in filtered result.

  - `true`: A shorthand for `function(actual, expected) { return angular.equals(expected, actual)}`.
    this is essentially strict comparison of expected and actual.

  - `false|undefined`: A short hand for a function which will look for a substring match in case
    insensitive way.

@example
   <example>
     <file name="index.html">
       <div ng-init="friends = [{name:'John', phone:'555-1276'},
                                {name:'Mary', phone:'800-BIG-MARY'},
                                {name:'Mike', phone:'555-4321'},
                                {name:'Adam', phone:'555-5678'},
                                {name:'Julie', phone:'555-8765'},
                                {name:'Juliette', phone:'555-5678'}]"></div>

       Search: <input ng-model="searchText">
       <table id="searchTextResults">
         <tr><th>Name</th><th>Phone</th></tr>
         <tr ng-repeat="friend in friends | filter:searchText">
           <td>{{friend.name}}</td>
           <td>{{friend.phone}}</td>
         </tr>
       </table>
       <hr>
       Any: <input ng-model="search.$"> <br>
       Name only <input ng-model="search.name"><br>
       Phone only <input ng-model="search.phone"><br>
       Equality <input type="checkbox" ng-model="strict"><br>
       <table id="searchObjResults">
         <tr><th>Name</th><th>Phone</th></tr>
         <tr ng-repeat="friendObj in friends | filter:search:strict">
           <td>{{friendObj.name}}</td>
           <td>{{friendObj.phone}}</td>
         </tr>
       </table>
     </file>
     <file name="protractor.js" type="protractor">
       var expectFriendNames = function(expectedNames, key) {
         element.all(by.repeater(key + ' in friends').column(key + '.name')).then(function(arr) {
           arr.forEach(function(wd, i) {
             expect(wd.getText()).toMatch(expectedNames[i]);
           });
         });
       };

       it('should search across all fields when filtering with a string', function() {
         var searchText = element(by.model('searchText'));
         searchText.clear();
         searchText.sendKeys('m');
         expectFriendNames(['Mary', 'Mike', 'Adam'], 'friend');

         searchText.clear();
         searchText.sendKeys('76');
         expectFriendNames(['John', 'Julie'], 'friend');
       });

       it('should search in specific fields when filtering with a predicate object', function() {
         var searchAny = element(by.model('search.$'));
         searchAny.clear();
         searchAny.sendKeys('i');
         expectFriendNames(['Mary', 'Mike', 'Julie', 'Juliette'], 'friendObj');
       });
       it('should use a equal comparison when comparator is true', function() {
         var searchName = element(by.model('search.name'));
         var strict = element(by.model('strict'));
         searchName.clear();
         searchName.sendKeys('Julie');
         strict.click();
         expectFriendNames(['Julie'], 'friendObj');
       });
     </file>
   </example>