Grouping values in array for summing up of values

JavaScript
1

Good day!

I need some help regarding grouping array values to get the summation.

I have an array like this:

ArrInput = [
{
“year”:2019,
“id”:“book”,
“price”:500.00
},
{
“year”:2019,
“id”:“magazine”,
“price”:300.00
},
{
“year”:2019,
“id”:“book”,
“price”:300.00
}
];

Is it possible to group the values to get the summation? Example is like this one:

ArrResult = [
{
“year”:2019,
“id”:“book”,
“price”:800.00
},
{
“year”:2019,
“id”:“magazine”,
“price”:300.00
}
]

3

Here’s a way, using reduce.

function combineItem(resultItem, item) {
    return {
        "year": Math.max(resultItem.year, item.year),
        "id": item.id,
        "price": resultItem.price + item.price
    };
}
function itemsReducer(resultItems, item) {
    const updateIndex = resultItems.findIndex(function(resultItem) {
        return resultItem.id === item.id;
    });
    if (updateIndex === -1) {
        return resultItems.concat(item);
    }
    resultItems[updateIndex] = combineItem(resultItems[updateIndex], item);
    return resultItems;
}
ArrResult = ArrInput.reduce(itemsReducer, []);

With the year I’ve decided to select the most recent year when adding them together.

2 Likes
4

Thank you very much for your help!

5

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