What is the best way to combine these arrays?

Having trouble finding the most efficient solution to this problem. I attempted using a loop, but I can't seem to make any progress. Any assistance would be greatly appreciated.

This is my current data:

[ [ ‘TWENTY’, 2000 ],
[ ‘TWENTY’, 2000 ],
[ ‘TWENTY’, 2000 ],
[ ‘TEN’, 1000 ],
[ ‘TEN’, 1000 ],
[ ‘FIVE’, 500 ],
[ ‘FIVE’, 500 ],
[ ‘FIVE’, 500 ],
[ ‘ONE’, 100 ],
[ ‘QUARTER’, 25 ],
[ ‘QUARTER’, 25 ],
[ ‘DIME’, 10 ],
[ ‘DIME’, 10 ],
[ ‘PENNY’, 1 ],
[ ‘PENNY’, 1 ],
[ ‘PENNY’, 1 ],
[ ‘PENNY’, 1 ] ]

I am aiming for:

[ [ ‘TWENTY’, 6000 ],
    [ ‘TEN’, 2000 ],
    [ ‘FIVE’, 1500 ],
    [ ‘ONE’, 100 ],
    [ ‘QUARTER’, 50 ],
    [ ‘DIME’, 20 ],
    [ ‘PENNY’, 4 ] ]

My attempt at solving it so far:

newArr = [ [ 'TWENTY', 0 ],
    [ 'TEN', 0 ],
    [ 'FIVE', 0 ],
    [ 'ONE', 0 ],
    [ 'QUARTER', 0 ],
    [ 'DIME', 0 ],
    [ 'PENNY', 0 ] ];

for (var z = 0; z < arr.length; z++) {
  for (var y = 0; y < newArr.length; y++) {
    if (newArr[y][0] == arr[z][0]) {
    newArr[y][1] =  newArr[y][1] + arr[z][1]
    }
  }

}
javascriptarrays

Answer №1

Check out the code snippet below for the solution:

const arr = [['TWENTY', 2000],
['TWENTY', 2000],
['TWENTY', 2000],
['TEN', 1000],
['TEN', 1000],
['FIVE', 500],
['FIVE', 500],
['FIVE', 500],
['ONE', 100],
['QUARTER', 25],
['QUARTER', 25],
['DIME', 10],
['DIME', 10],
['PENNY', 1],
['PENNY', 1],
['PENNY', 1],
['PENNY', 1]];

const b = arr.reduce((a,c) => {
    if (a.has(c[0])) {
        a.get(c[0])[1]+=c[1];
    } else {
        a.set(c[0],c);
    }
    return a;
},new Map());
console.log(b);

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