Javascript Multidimensional Array: Add Values

Question

So I have a multidimensional array like:

myArr = [["venue",2],["venue",16],["inning",2],["inning",4],["inning",32],["hithard", 4]]

I would like to add the similar values up. So in the end I just have:

"venue" = 18, "inning" = 38, and "hithard" = 4.

Can you give me an example of how to accomplish this? Either with Javascript and/or jQuery

Thanks!

Do you want an array or object? Object is { venue=18, inning=36, hithard=4} and Array is [["venue", 18], ["inning", 38], ["hithard", 4]] — Selvakumar Arumugam
– Selvakumar Arumugam, Commented May 7, 2012 at 19:52
Well I'm going to be turning this into a querystring to pass to a service so I'm sure either will work well — ksumarine
– ksumarine, Commented May 7, 2012 at 19:54
I'm going to add this to my list of interview questions, it's brought out a ton of interesting approaches — Mike Robinson
– Mike Robinson, Commented May 7, 2012 at 20:00
@Corey you can always use $.param to parse the obj to a query string. — Selvakumar Arumugam
– Selvakumar Arumugam, Commented May 7, 2012 at 20:11

Selvakumar Arumugam · Accepted Answer · 2012-05-07 19:54:23Z

3

I am not sure if you want an array or object. If object, stop it is 1st pass and tmp in below code should return you the object as Object { venue=18, inning=38, hithard=4}.

DEMO

var tmp = {}, keys;
for (var i = 0; i < myArr.length; i++) {
    keys = myArr[i][0];
    tmp[keys] = (tmp.hasOwnProperty(keys))? 
              (tmp[keys] + myArr[i][1]):myArr[i][1];
} //tmp - will return you a Object { venue=18, inning=38, hithard=4}

var output = [];
for (keys in tmp) {
    output.push([keys, tmp[keys]]);
} //output will return you an array as [["venue", 18],["inning", 38],["hithard", 4]]

edited May 7, 2012 at 19:54

answered May 7, 2012 at 19:43

Selvakumar Arumugam

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2 Comments

Gavriel Over a year ago

this doesn't have query string output, mine below does

Selvakumar Arumugam Over a year ago

@Gavriel OP mentions that he will be using it in query string. However initial post doesn't say anything about query string. Let say if he want this in AJAX data, then he can just use it right away..

Gavriel · Accepted Answer · 2012-05-07 19:55:33Z

3

myArr = [["venue",2],["venue",16],["inning",2],["inning",4],["inning",32],["hithard", 4]];
values = {};
for (i=0;i<myArr.length;i++){
   if ("undefined" == typeof values[myArr[i][0]]) {values[myArr[i][0]] = 0;}
   values[myArr[i][0]] += myArr[i][1];
}
arr = [];
query_string = "";
for (i in values) {
    // if you want it in an array:
    arr.push('"' + i + '" = ' + values[i]);
    query_string += (query_string.length ? "&" : "") + i + "=" + values[i];
}
console.log(arr);

DEMO: http://jsfiddle.net/Ta97E/2/

you can use values to create the query string

edited May 7, 2012 at 19:55

answered May 7, 2012 at 19:36

Gavriel

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4 Comments

Gavriel Over a year ago

what's wrong with it? This is dynamic and it sums them by category

C.S. Over a year ago

I see what you are going for here Gavriel. This solution goes toward the idea of not limiting your code to a static requirement. What if a fourth or fifth statistic was needed? by creating the object based on the key and then incrementing into that key value pair, this solves the problem. I would have approached it only slightly different. This does not deserve a down vote.

C.S. Over a year ago

@MikeRobinson Where in the question does he specify that the answer has to be an array result? That is a terrible assumption. The question effectively asks, "how do I add these three things up".

Mike Robinson Over a year ago

@ChristopherSmithson You have a point, I was just going with the idea of maintaining datatypes just in case there's part of the code further on that rely on this configuration.

VisioN · Accepted Answer · 2012-05-07 19:54:20Z

2

Check this code:

var final = {};
for (var i in myArr) {
    var item = myArr[i];
    final[item[0]] = (final[item[0]] || 0) + item[1];
}

console.log(final);

DEMO: http://jsfiddle.net/UVJEb/

edited May 7, 2012 at 19:54

answered May 7, 2012 at 19:43

VisioN

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3 Comments

Otto Allmendinger Over a year ago

strictly speaking it misses if (myArr.hasOwnProperty(i)), otherwise it would be a perfect general solution

VisioN Over a year ago

@OttoAllmendinger You mean final.hasOwnProperty? I think (final[item[0]] || 0) covers it absolutely. Can't imagine the situation when it won't work.

Otto Allmendinger Over a year ago

the hasOwnProperty check filters inherited properties: stackoverflow.com/a/86306/92493

Otto Allmendinger · Accepted Answer · 2012-05-07 19:54:55Z

2

Underscore solution:

 sums = _.reduce(myArr, function (obj, item) { 
    obj[item[0]] = (obj[item[0]] || 0) + item[1]; 
    return obj; 
 }, {});

 // sums = {"venue":18,"inning":38,"hithard":4}

A little dirtier in jQuery

sums = {}

$.each(myArr, function (i, value) {
    sums[value[0]] = (sums[value[0]] || 0) + value[1];
});

Edit: add jQuery version

edited May 7, 2012 at 19:54

answered May 7, 2012 at 19:44

Otto Allmendinger

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1 Comment

ksumarine Over a year ago

I like your dirty jQuery solution also. Thank you!

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