Allow angular to watch nested object properties in array

nestedWatch.js

$scope.chartBuilder = {
		charts: [{
			name: 'Gauge Chart',
			type: 'gauge',
			description: '',
			title: '',
			series: [{
				resultQueryType: "",
				resultQueryID: 0,
				resultQueryFactID: 0,
			}],
		}, ]
	};
	// watch the chart series data for updates and make the necessary updates
	$scope.$watchCollection('chartBuilder.charts', function(newCollection, oldCollection, scope) {
		for (var i = 0; i < newCollection.length; i++) {
			var expression =  'chartBuilder.charts['+i+'].series'
			$scope.$watch(expression, function(newValue, oldValue, scope) {
				console.log('Series Updated', newValue, oldValue);
			}, true);
		};
	});