Create a new array adding duplicate values together

Question

I have a two dimensional array:

[[bourbon, 2], [bourbon, 1],[scotch, 2]]

I would like to end up with a new array that consolidates the duplicates so that the array would become

 [[bourbon, 3], [scotch, 2]]

Here is how I create the array:

    for(var i=0; i< data.length; i++){
         var typeW = String(data[i].doc.type);
         var valueAsNumber = parseInt(data[i].doc.bottle);
         typeOfWhiskey[j,i] = [typeW,valueAsNumber];
         j++;
    }

I have tried to check for unique values with:if(typeOfWhiskey.indexOf(typeW ) > -1){

However I am currently stuck. In this example 'typeW' is the string value for 'bourbon', or 'scotch' for example, where as 'valueAsNumber' would be 2 or 1 based on the example provided. I would like to not have to create another for look and iterate through the whole array again because I feel that would be inefficient. I think I am close but am not sure how to proceed. Thanks

@FelixKling it is allowing me to construct the array. j and i increment as I more through the array where I get the values causing typeOfWhiskey to be built. — Alos
– Alos, Commented May 11, 2015 at 22:45
Mmh.... typeOfWhiskey[j,i] is eqivalent to typeOfWhiskey[i]. j,i is the comma operator at work, so the whole expression evaluates to i. You might want typeOfWhiskey[j][i] — Felix Kling
– Felix Kling, Commented May 11, 2015 at 22:46

Amit · Accepted Answer · 2015-05-11 22:59:36Z

1

This will work:

var source = [['bourbon', 2], ['bourbon', 1],['scotch', 2]];
var hash = {};
var consolidated = [];

source.forEach(function(item) {
     hash[item[0]] = (hash[item[0]] || 0) + item[1];
});

Object.keys(hash).forEach(function(key) {
     consolidated.push([key, hash[key]]);
});

jsFiddle

answered May 11, 2015 at 22:59

Amit

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Comments

Ronnie Smith · Accepted Answer · 2015-05-11 22:57:26Z

Create a copy of initial array.

I did something similar recently, this might help:

// Create copy to delete dups from
$copy = $sowArray; 
$sharedDescriptions = array();

for( $i=0; $i<count($sowArray); $i++ ) {
    if ( in_array( $sowArray[$i][$description], $sharedDescriptions ) ) {
        unset($copy[$i]);
    }
    else {
        $sharedDescriptions[] = $sowArray[$i][$description];
    }
}
$sharedDescriptions = array_values($sharedDescriptions);
$copy = array_values($copy);

// Update quantities of duplicate items
for( $i=0; $i<count($copy); $i++ ) {
    $product = $copy[$i][$description];
    $qty = 0;
    if (in_array($product, $sharedDescriptions)) {
        foreach ($sowArray as $sowRow) {
            if ($sowRow[$description] === $product){
                $qty += $sowRow[$quantity];
               }
            }
        $copy[$i][$quantity] = $qty;
        } 
    }

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