function TodoCtrl($scope){
var sums = $scope.sums = [];
$scope.sum = '200';
$scope.addSu = function(sum){
sums.push(sum);
};
$scope.removeSum = function(index){
sum.splice(index,1);
};
}<!DOCTYPE html>
<html>
<head>
<script src="http://code.angularjs.org/1.1.4/angular.min.js"></script>
<script src="todo.js"></script>
</head>
<body>
<div ng-app>
<div ng-controller="TodoCtrl">
<h2>Сегодня я потратил: {{sum}} руб.</h2>
<input type = 'text' ng-model = "sum" size = "40" />
<button ng-click = "addSu(sum)">Добавить</button>
<ul>
<li ng-repeat = "sum in sums track by $index">
<span ng-bind="$parent.$eval(sum)"></span>
<span>руб</span>
</li>
</ul>
</div>
</div>
</body>
</html>
this.total = this.sums.reduce((sum, i) => sum + i, 0);