How to sum all the values in one column of an inner array table in JavaScript?

Question

I have a fairly simple set of data which has an inner array stored in a variable named finances. The first array element is a header row of Month and Amount.

I need to calculate a sum of all the amounts. Where do I start?

var finances = [
['Month', 'Amount'],
['Jan-2010', 867884],
['Feb-2010', 984655],
['Mar-2010', 322013],
['Apr-2010', -69417],
['May-2010', 310503],
['Jun-2010', 522857],
['Jul-2010', 1033096],
['Aug-2010', 604885],
['Sep-2010', -216386],
['Oct-2010', 477532],
['Nov-2010', 893810],
['Dec-2010', -80353],
['Jan-2011', 779806],
['Feb-2011', -335203],
['Mar-2011', 697845],
['Apr-2011', 793163],
['May-2011', 485070],
['Jun-2011', 584122],
['Jul-2011', 62729],
['Aug-2011', 668179],
['Sep-2011', 899906],
['Oct-2011', 834719],
['Nov-2011', 132003],
['Dec-2011', 309978],
['Jan-2012', -755566],
['Feb-2012', 1170593],
['Mar-2012', 252788],
['Apr-2012', 1151518],
['May-2012', 817256],
['Jun-2012', 570757],
['Jul-2012', 506702],
['Aug-2012', -1022534],
['Sep-2012', 475062],
['Oct-2012', 779976],
['Nov-2012', 144175],
['Dec-2012', 542494],
['Jan-2013', 359333],
['Feb-2013', 321469],
['Mar-2013', 67780],
['Apr-2013', 471435],
['May-2013', 565603],
['Jun-2013', 872480],
['Jul-2013', 789480],
['Aug-2013', 999942],
['Sep-2013', -1196225],
['Oct-2013', 268997],
['Nov-2013', -687986],
['Dec-2013', 1150461],
['Jan-2014', 682458],
['Feb-2014', 617856],
['Mar-2014', 824098],
['Apr-2014', 581943],
['May-2014', 132864],
['Jun-2014', 448062],
['Jul-2014', 689161],
['Aug-2014', 800701],
['Sep-2014', 1166643],
['Oct-2014', 947333],
['Nov-2014', 578668],
['Dec-2014', 988505],
['Jan-2015', 1139715],
['Feb-2015', 1029471],
['Mar-2015', 687533],
['Apr-2015', -524626],
['May-2015', 158620],
['Jun-2015', 87795],
['Jul-2015', 423389],
['Aug-2015', 840723],
['Sep-2015', 568529],
['Oct-2015', 332067],
['Nov-2015', 989499],
['Dec-2015', 778237],
['Jan-2016', 650000],
['Feb-2016', -1100387],
['Mar-2016', -174946],
['Apr-2016', 757143],
['May-2016', 445709],
['Jun-2016', 712961],
['Jul-2016', -1163797],
['Aug-2016', 569899],
['Sep-2016', 768450],
['Oct-2016', 102685],
['Nov-2016', 795914],
['Dec-2016', 60988],
['Jan-2017', 138230],
['Feb-2017', 671099]
];

//Make the inner array into a table
console.table(finances);

// Count the number of rows in the table, and subtract 1 for the header row
var NumberOfMonths = finances.length - 1;
console.log(NumberOfMonths);

I used the table(finances) in the console to see that the data is appropriate to find a sum. I also did a NumberOfMonths variable to check that all parts of the data are included in the array.

"I have a fairly simple set of data" where does it come from? why does it contain this row ['Month', 'Amount'],? because now you have to deal with the fact that your data contains this row. Every time you want to do anything with finances you have to include a rule that ignores this specific row. — Thomas
– Thomas, Commented Dec 27, 2022 at 17:39
Thank you. The data is just a sample set for me to work with. I added the header row to make it clearer to me what I was working with. — Jon Garnett-Smith
– Jon Garnett-Smith, Commented Dec 27, 2022 at 18:08
Then better use objects: var finances = [ { month: 'Jan-2010', amount: 867884 }, { month: 'Feb-2010', amount: 984655 }, { month: 'Mar-2010', amount: 322013 }, ... ] — Thomas
– Thomas, Commented Dec 27, 2022 at 18:20

NZJL · Accepted Answer · 2022-12-27 17:07:30Z

1

Try this:

finances.slice(1).reduce((sum, arr) => sum + arr[1], 0);

answered Dec 27, 2022 at 17:07

NZJL

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2 Comments

Jon Garnett-Smith Over a year ago

If I remove the header row of data, we just change slice(1) to slice(0)?

Thomas Over a year ago

@JonGarnett-Smith if you remove the header row you don't need to slice at all. finances.reduce(...)

WiatroBosy · Accepted Answer · 2022-12-27 17:05:59Z

var finances = [
['Month', 'Amount'],
['Jan-2010', 867884],
['Feb-2010', 984655],
['Mar-2010', 322013],
['Apr-2010', -69417],
['May-2010', 310503],
['Jun-2010', 522857],
['Jul-2010', 1033096],
['Aug-2010', 604885],
['Sep-2010', -216386],
['Oct-2010', 477532],
['Nov-2010', 893810],
['Dec-2010', -80353],
['Jan-2011', 779806],
['Feb-2011', -335203],
['Mar-2011', 697845],
['Apr-2011', 793163],
['May-2011', 485070],
['Jun-2011', 584122],
['Jul-2011', 62729],
['Aug-2011', 668179],
['Sep-2011', 899906],
['Oct-2011', 834719],
['Nov-2011', 132003],
['Dec-2011', 309978],
['Jan-2012', -755566],
['Feb-2012', 1170593],
['Mar-2012', 252788],
['Apr-2012', 1151518],
['May-2012', 817256],
['Jun-2012', 570757],
['Jul-2012', 506702],
['Aug-2012', -1022534],
['Sep-2012', 475062],
['Oct-2012', 779976],
['Nov-2012', 144175],
['Dec-2012', 542494],
['Jan-2013', 359333],
['Feb-2013', 321469],
['Mar-2013', 67780],
['Apr-2013', 471435],
['May-2013', 565603],
['Jun-2013', 872480],
['Jul-2013', 789480],
['Aug-2013', 999942],
['Sep-2013', -1196225],
['Oct-2013', 268997],
['Nov-2013', -687986],
['Dec-2013', 1150461],
['Jan-2014', 682458],
['Feb-2014', 617856],
['Mar-2014', 824098],
['Apr-2014', 581943],
['May-2014', 132864],
['Jun-2014', 448062],
['Jul-2014', 689161],
['Aug-2014', 800701],
['Sep-2014', 1166643],
['Oct-2014', 947333],
['Nov-2014', 578668],
['Dec-2014', 988505],
['Jan-2015', 1139715],
['Feb-2015', 1029471],
['Mar-2015', 687533],
['Apr-2015', -524626],
['May-2015', 158620],
['Jun-2015', 87795],
['Jul-2015', 423389],
['Aug-2015', 840723],
['Sep-2015', 568529],
['Oct-2015', 332067],
['Nov-2015', 989499],
['Dec-2015', 778237],
['Jan-2016', 650000],
['Feb-2016', -1100387],
['Mar-2016', -174946],
['Apr-2016', 757143],
['May-2016', 445709],
['Jun-2016', 712961],
['Jul-2016', -1163797],
['Aug-2016', 569899],
['Sep-2016', 768450],
['Oct-2016', 102685],
['Nov-2016', 795914],
['Dec-2016', 60988],
['Jan-2017', 138230],
['Feb-2017', 671090]
];

let numOr0 = n => isNaN(n) ? 0 : n

console.log(
  finances.reduce((a, b) => 
    numOr0(a) + numOr0(b[1]))
)

try this solution - it's just an example of how to do it

Omar Atri · Accepted Answer · 2022-12-27 17:00:36Z

0

Just iterate through the inner arrays and calculate the sum of the second elements.

function sumAmount(finance){
    let sum = 0;
    for (let row of finance){
        sum += row[1];
    }
    return sum;
}

answered Dec 27, 2022 at 17:00

Omar Atri

2502 silver badges8 bronze badges

2 Comments

Thomas Over a year ago

Check it yourself, I get there some "weird" result.

Omar Atri Over a year ago

Maybe because you passed the array as it is .. you should remove the first row because it contains a string. You can remove it with finance.slice(1). That means call the function like this: console.log( sumAmount( finance.slice(1) ) );

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