Sum values from an array of key-value pairs in JavaScript

Question

I have defined a JavaScript variables called myData which is a new Array like this:

var myData = new Array(['2013-01-22', 0], ['2013-01-29', 0], ['2013-02-05', 0],
             ['2013-02-12', 0], ['2013-02-19', 0], ['2013-02-26', 0], 
             ['2013-03-05', 0], ['2013-03-12', 0], ['2013-03-19', 0], 
             ['2013-03-26', 0], ['2013-04-02', 21], ['2013-04-09', 2]);

I am wondering if it is possible to sum the number values found in the array (ex. 0+0+21+2+0 and so on) and have probably a variable with the result that I can use outside of the script tag because I have 7 of this kind of arrays corresponding for each of the day in the week. I want to make a comparison afterwards based on that. That is the most preferred method for this kind of actions if is possible?

Iterate over the array and add the second elements of the inner arrays. — Felix Kling
– Felix Kling, Commented Apr 17, 2013 at 10:31

KooiInc · Accepted Answer · 2018-10-07 09:00:45Z

107

You could use the Array.reduce method:

const myData = [
  ['2013-01-22', 0], ['2013-01-29', 0], ['2013-02-05', 0],
  ['2013-02-12', 0], ['2013-02-19', 0], ['2013-02-26', 0], 
  ['2013-03-05', 0], ['2013-03-12', 0], ['2013-03-19', 0], 
  ['2013-03-26', 0], ['2013-04-02', 21], ['2013-04-09', 2]
];
const sum = myData
  .map( v => v[1] )                                
  .reduce( (sum, current) => sum + current, 0 );
  
console.log(sum);

See MDN

edited Oct 7, 2018 at 9:00

answered Apr 17, 2013 at 10:38

KooiInc

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4 Comments

VisioN Over a year ago

It should be prev[1] I guess. By all means the result won't give 23.

Mark Walters Over a year ago

@Kooilnc Please be aware that Array.reduce is an ECMAscript 5 addition so my not be supported by all browsers - see here developer.mozilla.org/en-US/docs/JavaScript/Reference/… which also includes some code which can be implemented to overcome this

KooiInc Over a year ago

@VisioN: forgot the initial value, added it. And no, it shouldn't be prev[1] @MarkWalters: yep, but one can use the shim from the MDN-link (see answer)

rjmunro Over a year ago

With an ES6 arrow function: var sum = myData.reduce((sum, current) => (sum + current[1]), 0);

ruhanbidart · Accepted Answer · 2014-12-16 01:15:45Z

58

I think the simplest way might be:

values.reduce(function(a, b){return a+b;})

answered Dec 16, 2014 at 1:15

ruhanbidart

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4 Comments

netpoetica Over a year ago

This should be the accepted answer to the general question asked, but the poster had a data structure that would not work with this unfortunately. This is accurately the best way to handle an array of numbers though

Nelfo Over a year ago

Ensuring they are numbers wouldn't hurt: values.reduce(function(a, b){return +a + +b;})

Paolo Moretti Over a year ago

@netpoetica myData.map(function(o) { return o[1]; }).reduce(a, b) { return a + b; })

hildende Over a year ago

With EC6 this could look like values.reduce((a + b) => a + b)

jesterjunk · Accepted Answer · 2015-05-11 10:03:46Z

18

Try the following

var myData = [['2013-01-22', 0], ['2013-01-29', 1], ['2013-02-05', 21]];

var myTotal = 0;  // Variable to hold your total

for(var i = 0, len = myData.length; i < len; i++) {
    myTotal += myData[i][1];  // Iterate over your first array and then grab the second element add the values up
}

document.write(myTotal); // 22 in this instance

edited May 11, 2015 at 10:03

jesterjunk

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answered Apr 17, 2013 at 10:33

Mark Walters

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6 Comments

Felix Kling Over a year ago

I think you meant myData[i][1]. And why use parseFloat if the value is already a number anyway?

Daniela costina Vaduva Over a year ago

it output 24156 instead of like it should 3. I've tested with an "empty value array" and I receive the same output...

Daniela costina Vaduva Over a year ago

@FelixKling it works with myData[i][1] but how I make myTotal available in other script tag?

Silas Hansen Over a year ago

Daniel, did you fix the typo that Felix Kling pointed out? Rember to write "myData[i][1]" instead of the wrong version: "myData[1]" in the example.

Mark Walters Over a year ago

@FelixKling Thanks have edited, and i guess i was being overprecautius by using parseFloat. Daniela i've tested and it works have a look here - jsbin.com/ibajas/1

|

Xotic750 · Accepted Answer · 2013-04-17 10:53:07Z

13

I would use reduce

var myData = new Array(['2013-01-22', 0], ['2013-01-29', 0], ['2013-02-05', 0], ['2013-02-12', 0], ['2013-02-19', 0], ['2013-02-26', 0], ['2013-03-05', 0], ['2013-03-12', 0], ['2013-03-19', 0], ['2013-03-26', 0], ['2013-04-02', 21], ['2013-04-09', 2]);

var sum = myData.reduce(function(a, b) {
    return a + b[1];
}, 0);

$("#result").text(sum);

Available on jsfiddle

answered Apr 17, 2013 at 10:53

Xotic750

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Comments

lee penkman · Accepted Answer · 2015-05-19 05:35:04Z

Creating a sum method would work nicely, e.g. you could add the sum function to Array

Array.prototype.sum = function(selector) {
    if (typeof selector !== 'function') {
        selector = function(item) {
            return item;
        }
    }
    var sum = 0;
    for (var i = 0; i < this.length; i++) {
        sum += parseFloat(selector(this[i]));
    }
    return sum;
};

then you could do

> [1,2,3].sum()
6

and in your case

> myData.sum(function(item) { return item[1]; });
23

Edit: Extending the builtins can be frowned upon because if everyone did it we would get things unexpectedly overriding each other (namespace collisions). you could add the sum function to some module and accept an array as an argument if you like. that could mean changing the signature to myModule.sum = function(arr, selector) { then this would become arr

Jan Jarčík · Accepted Answer · 2016-10-04 15:00:16Z

8

Or in ES6

values.reduce((a, b) => a + b),

example:

[1,2,3].reduce((a, b)=>a+b) // return 6

answered Oct 4, 2016 at 15:00

Jan Jarčík

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Comments

r3wt · Accepted Answer · 2015-12-07 11:08:35Z

2

If you want to discard the array at the same time as summing, you could do (say, stack is the array):

var stack = [1,2,3],
    sum = 0;
while(stack.length > 0) { sum += stack.pop() };

edited Dec 7, 2015 at 11:08

r3wt

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answered Feb 7, 2014 at 4:24

btk

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Comments

bjhamltn · Accepted Answer · 2015-12-31 03:41:14Z

1

You can use the native map method for Arrays. map Method (Array) (JavaScript)

var myData = new Array(['2013-01-22', 0], ['2013-01-29', 0], ['2013-02-05', 0],
             ['2013-02-12', 0], ['2013-02-19', 0], ['2013-02-26', 0], 
             ['2013-03-05', 0], ['2013-03-12', 0], ['2013-03-19', 0], 
             ['2013-03-26', 0], ['2013-04-02', 21], ['2013-04-09', 2]);
var a = 0;
myData.map( function(aa){ a += aa[1];  return a; });

a is your result

edited Dec 31, 2015 at 3:41

answered Dec 31, 2015 at 3:36

bjhamltn

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Comments

Shahid Islam · Accepted Answer · 2021-01-19 21:18:19Z

1

where 0 is initial value

Array.reduce((currentValue, value) => currentValue +value,0)

or

Array.reduce((currentValue, value) =>{ return currentValue +value},0)

or

[1,3,4].reduce(function(currentValue, value) { return currentValue + value},0)

answered Jan 19, 2021 at 21:18

Shahid Islam

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Comments

Gismo Ranas · Accepted Answer · 2013-11-11 17:35:14Z

0

The javascript built-in reduce for Arrays is not a standard, but you can use underscore.js:

var data = _.range(10);
var sum = _(data).reduce(function(memo, i) {return memo + i});

which becomes

var sumMyData = _(myData).reduce(function(memo, i) {return memo + i[1]}, 0);

for your case. Have a look at this fiddle also.

answered Nov 11, 2013 at 17:35

Gismo Ranas

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Comments

Musa · Accepted Answer · 2017-03-06 15:16:41Z

0

Old way (if you don't now the length of arguments/parameters)

 >> function sumla1(){

    result=0
    for(let i=0; i<arguments.length;i++){

        result+=arguments[i];

    }
    return result;
    }
    >> sumla1(45,67,88);
    >> 200

ES6 (destructuring of array)

>> function sumla2(...x){return x.reduce((a,b)=>a+b)}
>>
>> sumla2(5,5,6,7,8)
>>
>> 31
>>
>> var numbers = [4, 9, 16, 25];
>> sumla2(...numbers);
>> 54

edited Mar 6, 2017 at 15:16

answered Mar 6, 2017 at 14:12

Musa

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