sort it out in angular

sortable.js

/**
 * @ngdoc directive
 * @name sortable
 * @restrict A
 * 
 * @description
 * setup an object on the scope for handling a list: sorting, filtering, etc
 * NOTE that track by statements must go at the end of the expression, after the orderBy statement
 *  
 * @example
    <table sortable ng-init="columns=3; data=[{name:'Bill',color:'Brown',id:1}, {name:'Bob',color:'Green',id:3}, {name:'Bertha',color:'Blue',id:5}, {name:'Bob',color:'Yellow',id:9}]">'
      <thead>
        <tr><th colspan="{{ columns }}">
          <input type=text ng-model="sortable.filter" placeholder="filter">
          <input min={{sortable.min}} max={{sortable.max}} type=number title="max ({{sortable.min}}-{{sortable.max}})" ng-model="sortable.limit" >
        </th></tr>
        <tr>
            <th ng-click="sortable.sortBy(key);" ng-repeat="(key, value) in data[0] track by $index">{{ key }}</th>'
        </tr>
      <thead>
      <tbody>
        <tr ng-repeat="item in data | filter: sortable.filter | limitTo: sortable.limit | orderBy: [sortable.field, 'id'] : sortable.reverse track by $index">'
            <td ng-repeat="(key, value) in item" class="{{key}}">{{ value }}</td>'
        </tr>
     </tbody>
   </table>
 * 
 */
.directive('sortable', function(){
    return {
        restrict: 'A'
        ,controller: function($scope){
/**
 * @ngdoc object
 * @name sortable
 * @description
 * an object with properties conveniently places on the current scope (for manipulating a collection)
 * add new properties or use existing ones for filtering, limiting, ordering
 * 
 * @param { function } sortBy for handling toggling the sortable.field string through 3 options 'key', '-key', '' which are sorting by key, reversing it, turning it back off
 * @param { string } filter for filtering
 * @param { integer } min limiting
 * @param { integer } max limiting
 * @param { boolean } reverse for flipping the sorting
 * @param { string } field for ordering, any value, sortBy toggles it through the 3 options '', 'key', '-key'
 * 
 */
            $scope.sortable = {
                filter: ''
                ,limit: 100
                ,min: 10
                ,max: 10000
                ,reverse: false
                ,field: ''
                ,sortBy: function sortBySetup(key){
                    var _key;
                    if(!key) return;
                    switch( this.field ){
                    case '-'+key:
                        // cycle back off
                        _key = '';
                    break;
                    case key:
                        // reverse by key
                        _key = '-'+key;
                    break;
                    default:
                        // order by key
                        _key = key;
                    }
                    this.field = _key;
                }
            };
        }
    }
})
;

/* unit test */
describe('sortable', function(){
	var scope, element, i = 0, sortable;
	beforeEach( inject(function($injector, $rootScope, $compile){
			scope = $rootScope.$new();
			scope.list = [1,2,3,4,5];
			element = $compile('<table sortable data="list"></table>')(scope);
			scope.$digest();
	}) );
	it('should create an object on the scope', function(){		
			//sortable = element.find('table').scope().sortable;
			sortable = element.scope().sortable;
			expect( sortable.limit ).toBe( 100 );
			expect( sortable.min ).toBe( 10 );
			expect( sortable.reverse ).toBe( false );
			// cycle thru possibilities
			sortable.sortBy('key');
			expect( sortable.field ).toBe( 'key' );
			sortable.sortBy('key');
			expect( sortable.field ).toBe( '-key' );

			sortable.sortBy();
			// unchanged by empty
			expect( sortable.field ).toBe( '-key' );

			sortable.sortBy('key');
			expect( sortable.field ).toBe( '' );
	});
})
;