Aggregate object properties in JavaScript

Question

I would like to aggregate properties in an array of objects and produce another object with totals.

Here is an example of what I'm working on:

Below is an array of the objects, and we need to sum displayAd_imp, videoAd_imp, tv_impbased on WeekNo range.

var objArr = [{

    "Title": "July 13 - July 19 2014",
    "displayAd_imp": "15",
    "videoAd_imp": "75",
    "tv_imp": "120",
    "Date": "2014-07-17T00:00:00.000Z",
    "WeekNo": 29
}, {

    "Title": "July 20 - July 26 2014",
    "displayAd_imp": "25",
    "videoAd_imp": "65",
    "tv_imp": "130",
    "Date": "2014-07-24T00:00:00.000Z",
    "WeekNo": 30
}, {

    "Title": "July 27 - Aug 2 2014",
    "displayAd_imp": "35",
    "videoAd_imp": "55",
    "tv_imp": "140",
    "Date": "2014-07-31T00:00:00.000Z",
    "WeekNo": 31
}, {

    "Title": "Aug 3 - Aug 9 2014",
    "displayAd_imp": "55",
    "videoAd_imp": "25",
    "tv_imp": "20",
    "Date": "2014-08-07T00:00:00.000Z",
    "WeekNo": 32
}, {

    "Title": "Aug 10 - Aug 17 2014",
    "displayAd_imp": "10",
    "videoAd_imp": "70",
    "tv_imp": "120",
    "Date": "2014-08-14T00:00:00.000Z",
    "WeekNo": 33
}]

The function below gets the range. We pass data, start-week, and end-week as params and it filters the data by desired range. I have a JSfiddle example to show the output.

function CalcWeekRange(data,begin,end){
    console.log(data,begin, end);
     newArr = data.filter(function(item){
        return (item.WeekNo >= begin && item.WeekNo <= end);
    });
    console.log(newArr); 

}

After this I need to sum up the result into an object that would look something like:

    {
        "displayAd_imp": "140",
        "videoAd_imp": "290",
        "tv_imp": "530",
    }

The last part is where I'm stuck :(

Hope I made the question clear, thanks in advance!

look at the reduce function, awesome for this use case.

bitoiu
– bitoiu

2014-08-20 19:00:10 +00:00
Commented Aug 20, 2014 at 19:00 — bitoiu
– bitoiu, Commented Aug 20, 2014 at 19:00

elclanrs · Accepted Answer · 2014-08-20 19:07:42Z

1

You can use reduce with an initial accumulator:

function weekRange(begin, end, data) {
  return data.filter(function(x) {
    return x.WeekNo >= begin && x.WeekNo <= end;
  }).reduce(function(acc, x) {
    Object.keys(acc).forEach(function(k) {
      acc[k] += Number(x[k]);
    });
    return acc;
  },{
    displayAd_imp: 0,
    videoAd_imp: 0,
    tv_imp: 0
  });
}

answered Aug 20, 2014 at 19:07

elclanrs

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3 Comments

habibg Over a year ago

Thanks for the quick response! The above snippet is returning NaN - "{displayAd_imp: NaN, videoAd_imp: NaN, tv_imp: NaN}". Perhaps I may be doing something wrong. I made a jsfiddle in the above post, please feel free to use that to project.

habibg Over a year ago

That's interesting, I see why the numbers were not working for me. the properties had a different format. I have updated jsfiddle.net/64gcjLku/9. The Number(x[k]) can't read the value since it contains ",". I will try to look into this.

habibg Over a year ago

Updated jsfiddle.net/64gcjLku/10. It should now support the above format as well. THANKS EVERYONE!!

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