Calculate in ng-repeat from the entry before - angularjs

Question

I have a filtered list (which is filtered by time - so in a specific timeframe) and over these item I am iterating with ng-repeat. These items have a name and a price. So if I am iterating over them I want to achieve that I always show the "sub"-total like this:
DATE NAME PRICE SUBTOTAL
2014-05 T-Shirt 20.00 20.00
2014-05 Jeans 45.00 65.00
2014-05 Cap 15.00 80.00
These Items are sorted by date but might have a different ID (ids dont match the index!).
I am really not able to find out how I could always calculate the subtotal (the table can be filtered by date ranges, means I could also include the items from 2014-04 and it should recalculate dynamically.
I tried it with a function like this in the controller:
var curBalanceCounter2 = 0;
$scope.currentBalanceCalc = function(finance) {
curBalanceCounter2 = curBalanceCounter2 + finance.amount;
return curBalanceCounter2;
}
But this i being executed 10 times so I get wrong numbers. Any better solution?
Thank you.

Answer 1

Create a custom filter
myApp.filter('subtotal', function(){
return function(items, index){
var subtotal = 0;
for (var i = 0; i <= index; i++) {
subtotal += items[i].price
}
return subtotal || items[index].price;
}
});
and call it like so
<li ng-repeat="item in items">{{item.name}} - {{item.price}} -
{{ items | subtotal : $index}}</li>
Demo
Since you have access to the original list (e.g. items in the code above) inside of an ng-repeat, you can pass it, along with the index of the current item, into a custom filter. This filter can then loop through each item up to and including the index passed in, and then return a summed subtotal. If the subtotal is 0 (as it would be for a first item), instead return the price of that item.
Docs: Custom filters in Angular

Answer 2

This is similar to Marc's answer. Define a subtotal function in the controller:
$scope.subtotal = function(index){
var total = 0;
angular.forEach($scope.data, function(value, key){
if(key <= index)
total += value.Price;
});
return total;
}
Then use it like this in the view:
<tr ng-repeat="d in data">
<td>{{d.Date}}</td>
<td>{{d.Name}}</td>
<td>{{d.Price}}</td>
<td>{{subtotal($index)}}</td>
</tr>
Demo
Update
If the issue is that the data isn't already sorted on the client, but is being sorted by a filter on the ng-repeat, then here's the fix:
Pass in the orderBy parameter to the subtotal function, and execute the filter on the data before computing the subtotals:
$scope.orderBy = 'Date';
$scope.subtotal = function(index, orderBy){
var total = 0;
angular.forEach($filter('orderBy')($scope.data,orderBy), function(value, key){
if(key <= index)
total += value.Price;
});
return total;
}
I've updated my demo with this code. You can change the sort order by changing 'Date' to 'Name' or 'Price' on this line
$scope.orderBy = 'Date';
and see that the subtotals automatically recalculate.

Answer 3

I don't know of a way to do this in pure angular, perhaps someone will chime in.
What you need looks like a cumulative sum:
function cSum(arr) {
var cumsum = [];
for(var i=0;i<arr.length;i++) {
if(i==0) cumsum[i] = arr[0];
else cumsum[i] = cumsum[i-1] + arr[i];
}
return cumsum
}
Then just add that field into the array of objects that you are repeating over and you can display it in the table.

Answer 4

Not too hard to do http://jsfiddle.net/VAJ5S/3/
HTML
<div ng-app="myApp">
<table ng-controller="myController">
<thead>
<tr>
<th>DATE</th>
<th>NAME</th>
<th>PRICE</th>
<th>SUBTOTAL</th>
</tr>
</thead>
<tr ng-repeat="item in items">
<td>{{item.date}}</td>
<td>{{item.name}}</td>
<td>{{item.price}}</td>
<td>{{subtotal($index)}}</td>
</tr>
</table>
</div>
JS
var app = angular.module("myApp", []);
app.controller("myController", ["$scope", function($scope){
$scope.items = [
{
date: "2014-05",
name: "T-Shirt",
price: 20.00
},
{
date: "2014-05",
name: "Jeans",
price: 65.00
},
{
date: "2014-05",
name: "Cap",
price: 80.00
}
];
$scope.subtotal = function(ind){
var subtotal = 0;
for (var i = 0; i<=ind; i++){
subtotal += $scope.items[i].price;
}
return subtotal;
};
}]);