Calculating Summing value from object based on array and updating same with total

Question

I have an object with basically three important parameters I need to for total calculation. So for example my object is as below :

[
{'Id':1,'ResourceId':1,'StartDate':'01-01-2017','Hours':8,'TotalHrs':8},
{'Id':2,'ResourceId':1,'StartDate':'01-01-2017','Hours':4,'TotalHrs':4},
{'Id':3,'ResourceId':1,'StartDate':'01-03-2017','Hours':4,'TotalHrs':4},
{'Id':4,'ResourceId':1,'StartDate':'01-03-2017','Hours':4,'TotalHrs':4},
{'Id':5,'ResourceId':2,'StartDate':'01-01-2017','Hours':2,'TotalHrs':2},
{'Id':6,'ResourceId':2,'StartDate':'01-01-2017','Hours':4,'TotalHrs':4},
{'Id':7,'ResourceId':2,'StartDate':'01-03-2017','Hours':2,'TotalHrs':2},
]

So, currently the TotalHrs parameter is of the same value as the Hours parameter.

I want it to be total for a particular ResourceId and Startdate. i.e If in the array if the ResourceId and Startdate matches the TotalHrs parameter should be total of the value from Hours parameter.

So the final array becomes.

[
{'Id':1,'ResourceId':1,'StartDate':'01-01-2017','Hours':8,'TotalHrs':12},
{'Id':2,'ResourceId':1,'StartDate':'01-01-2017','Hours':4,'TotalHrs':12},
{'Id':3,'ResourceId':1,'StartDate':'01-03-2017','Hours':4,'TotalHrs':8},
{'Id':4,'ResourceId':1,'StartDate':'01-03-2017','Hours':4,'TotalHrs':8},
{'Id':5,'ResourceId':2,'StartDate':'01-01-2017','Hours':2,'TotalHrs':6},
{'Id':6,'ResourceId':2,'StartDate':'01-01-2017','Hours':4,'TotalHrs':6},
{'Id':7,'ResourceId':2,'StartDate':'01-03-2017','Hours':2,'TotalHrs':2},
]

Hence in the above example, ResourceId : 1 and StartDate : 01-01-2017 has two occurrences with Hours value as 8 and 4, so there TotalHrs becomes 8+4=12.

Also, I don't want to group by, I want the same number of elements in the resulting array but with an updated value for TotalHrs.

Possible duplicate of [What is the most efficient method to groupby on a javascript array of objects?](http://stackoverflow.com/questions/14446511/what-is-the-most-efficient-method-to-groupby-on-a-javascript-array-of-objects) — George, Feb 21 '17 at 11:36
@RomanPerekhrest, its not the date format exactly, its the String.I do need to use it this way for the sake of application. — Mukta, Feb 21 '17 at 11:48
@Mukta, do you want to obtain a new array or to modify the initial array in place? — RomanPerekhrest, Feb 21 '17 at 11:49

score 0 · Answer 1 · answered Feb 21 '17 at 11:59

Short solution using Array.prototype.reduce() and Array.prototype.forEach() functions:

var data = [ {'Id':1,'ResourceId':1,'StartDate':'01-01-2017','Hours':8,'TotalHrs':8}, {'Id':2,'ResourceId':1,'StartDate':'01-01-2017','Hours':4,'TotalHrs':4}, {'Id':3,'ResourceId':1,'StartDate':'01-03-2017','Hours':4,'TotalHrs':4}, {'Id':4,'ResourceId':1,'StartDate':'01-03-2017','Hours':4,'TotalHrs':4}, {'Id':5,'ResourceId':2,'StartDate':'01-01-2017','Hours':2,'TotalHrs':2}, {'Id':6,'ResourceId':2,'StartDate':'01-01-2017','Hours':4,'TotalHrs':4}, {'Id':7,'ResourceId':2,'StartDate':'01-03-2017','Hours':2,'TotalHrs':2} ];

data.forEach(function (o) {
    o.TotalHrs = this[o.ResourceId + o.StartDate];
}, data.reduce(function (r, o) {
    var k = o.ResourceId + o.StartDate;
    (!r[k])? r[k] = o.TotalHrs : r[k] += o.TotalHrs;
    return r;
}, {}));

console.log(data);

var k = o.ResourceId + o.StartDate; - k here is a hash key string for grouping entries with same ResourceId and StartDate attributes

Apostolidis · Answer 2 · 2017-02-21T13:03:44.690

I suggest to use a temporary object, using the StartDate and ResourceId as hash key, that will store the hours. This algorithm providers O(n) time complexity.

var data = [{'Id':1,'ResourceId':1,'StartDate':'01-01-2017','Hours':8},{'Id':2,'ResourceId':1,'StartDate':'01-01-2017','Hours':4},{'Id':3,'ResourceId':1,'StartDate':'01-03-2017','Hours':4},{'Id':4,'ResourceId':1,'StartDate':'01-03-2017','Hours':4},{'Id':5,'ResourceId':2,'StartDate':'01-01-2017','Hours':2},{'Id':6,'ResourceId':2,'StartDate':'01-01-2017','Hours':4},{'Id':7,'ResourceId':2,'StartDate':'01-03-2017','Hours':2}];

function populateTotalHrs(collection) {
  var collectionByHash = {};
  collection.forEach(function(obj) {
    var hash = obj.ResourceId + '_' + obj.StartDate;
    collectionByHash[hash] = collectionByHash[hash] || 0;
    collectionByHash[hash] += obj.Hours;
  });
  collection.forEach(function(obj) {
    var hash = obj.ResourceId + '_' + obj.StartDate;
    obj.TotalHrs = collectionByHash[hash];
  });  
}

populateTotalHrs(data);
console.log(data);

Nina Scholz · Answer 3 · 2017-02-21T12:13:15.347

You could use a hash table and group it temporary by ResourceId and StartDate.

var data = [{ Id: 1, ResourceId: 1, StartDate: '01-01-2017', Hours: 8, TotalHrs: 8 }, { Id: 2, ResourceId: 1, StartDate: '01-01-2017', Hours: 4, TotalHrs: 4 }, { Id: 3, ResourceId: 1, StartDate: '01-03-2017', Hours: 4, TotalHrs: 4 }, { Id: 4, ResourceId: 1, StartDate: '01-03-2017', Hours: 4, TotalHrs: 4 }, { Id: 5, ResourceId: 2, StartDate: '01-01-2017', Hours: 2, TotalHrs: 2 }, { Id: 6, ResourceId: 2, StartDate: '01-01-2017', Hours: 4, TotalHrs: 4 }, { Id: 7, ResourceId: 2, StartDate: '01-03-2017', Hours: 2, TotalHrs: 2 }];

data.forEach(function (hash) {
    return function (a) {
        var key = [a.ResourceId, a.StartDate].join('|');
        if (!hash[key]) {
            hash[key] = [a];
            return;
        }
        hash[key].push(a);
        hash[key][0].TotalHrs += a.Hours;
        hash[key].forEach(function (b) {
            b.TotalHrs = hash[key][0].TotalHrs;
        });
    };
}(Object.create(null)));

console.log(data);

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Calculating Summing value from object based on array and updating same with total

3 Answers3