How to add number of days to existing ng-module date in angularjs?

Question

Hi all I'm new to angularjs actually i'm trying to add one ng-module value into another ng-moudule date input in angularjs... For exmaple:- 17-08-2016 add 20 Result Expecting 03-09-2016. my plunk

i don't know where i did the mistake and how to get the solution, please if anyone knows the answer help me for the same thanks.

My controller

 $scope.name = {
"_id": "57ac1b6d82e1c5940ac3c730",
"user": {
"_id": "57400c32bd07906c1308e2cf",
"displayName": "mani selvam"
},
"__v": 0,
"terms": "20",
"invoice_date": "2016-08-17",
"due_date": ""
};

Date.prototype.addDays = function(days) {
    this.setDate(this.getDate() + parseInt(terms));
    return this;
};

My Html:-

 <tr ng-repeat="mani in name"> </tr>
      <td >{{name.invoice_date | date:'dd-MM-yyyy'}}</td>
          <td >{{name.terms }}</td>
             <td >{{name.invoice_date | date:'dd-MM-yyyy'}} + {{name.terms }}</td>

Answer 1

You can fix it by doing this:

var app = angular.module('plunker', []);

app.controller('MainCtrl', function($scope) {
  $scope.name = {
"_id": "57ac1b6d82e1c5940ac3c730",
"user": {
"_id": "57400c32bd07906c1308e2cf",
"displayName": "mani selvam"
},
"__v": 0,
"terms": "20",
"invoice_date": "2016-08-17",
"due_date": ""
};

$scope.addDays = function(stringDate,days) {
   var date = new Date(stringDate);
   date.setDate(date.getDate() + parseInt(days));
  return date;
}

});

then in your template do:

 <td >{{addDays(name.invoice_date,name.terms) | date:'dd-MM-yyyy'}}</td>

the reason why something like this doesn't work in your example:

<td >{{(name.invoice_date | date:'dd-MM-yyyy').addDays({{name.terms}})}} + {{name.terms }}</td>

is because the angular date filter returns a String representation and thus is not linked to the date prototype

in theory this could work if your name.invoice_date would be a date object instead of a string in your json. take a look at this from the angular filter source code

@param {(Date|number|string)} date Date to format either as Date object, milliseconds (string or
 *    number) or various ISO 8601 datetime string formats (e.g. yyyy-MM-ddTHH:mm:ss.sssZ and its
 *    shorter versions like yyyy-MM-ddTHH:mmZ, yyyy-MM-dd or yyyyMMddTHHmmssZ). If no timezone is
 *    specified in the string input, the time is considered to be in the local timezone.

so if it would be a date to begin with you could do:

<td >{{(name.invoice_date).addDays({{name.terms}}) | date:'dd-MM-yyyy'}} + {{name.terms }}</td>